Excitons in epitaxially grown WS2 on Graphene: a nanometer-resolved EELS and DFT study

In this study, we investigate excitonic properties of epitaxially grown WS2, which is of particular interest for various applications due to its potential for upscaling to wafer sized structures. Understanding the effect of the dielectric environment due to changing layer numbers and multi-material heterostructures on the optical properties is crucial for tailoring device properties. Monochromated electron energy loss spectroscopy in a scanning transmission electron microscope is employed to characterize the excitonic spectrum of WS2 on graphene grown by metal organic chemical vapor deposition. This technique provides the required spatial resolution at the nanometer scale in combination with high quality spectra. To complement the experimental results, theoretical investigations using density functional theory and applying the Bethe-Salpeter equations are conducted. We find that by transitioning from mono- to bi- to multilayers of WS2 the spectra show redshifts for both, the K-valley excitons at about 2.0 and 2.4 eV as well as excitonic features of higher energies. The latter features originate from so called band nesting of transitions between the Gamma- and K-point. In summary, this study provides valuable insights into the excitonic properties of WS2 in different layer configurations and environments, which are realistically needed for future device fabrication and property tuning. Finally, we can show that nanometer scale electron spectroscopy supported by careful theoretical modelling can successfully link atomic structure and optical properties, such as exciton shifts, in non-idealized complex material systems like multilayer 2D heterostructures.Comment: 8 pages, 5 figure

Correction of Double-Chambered Right Ventricle 40 Years after Pulmonary Valvuloplasty

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Suture less Perceval Aortic Valve in Comparison with the Stented Carpentier-Edwards Perimount Aortic Valve

Background and aim of the study: The Sorin Perceval S (SP) sutureless bioprosthesis was developed as an advancement of conventional biological aortic valve replacement (AVR) with stented bioprostheses, and perhaps also as an alternative to the transcatheter aortic valve implantation (TAVI) procedure, especially for high-risk patients. Herein are described the authors' early results with SP valve replacement, compared to AVR with Carpentier-Edwards Perimount (EP) stented valves. Methods: Between September 2012 and February 2013, a total of 14 patients was enrolled in a single-center SP study group, and their data were analyzed in a prospective manner. For comparison, 14 patients who received an EP valve replacement during the same period were matched with the SP group, in a retrospective manner. Hemodynamic parameters and clinical outcome were monitored until discharge of the patients in order to analyze the early results of the two groups. Results: The cardiopulmonary bypass (CPB) and aortic cross-clamp (ACC) times needed for AVR with SP valves were significantly shorter than with EP valves. The mean CPB time for SP valve replacement without concomitant procedures was 58.4 +/- 11.0 min, compared to 71.8 +/- 11.3 min in the EP group (p = 0.015), while the mean ACC times were 37.3 +/- 6.8 and 49.1 +/- 11.2 min, respectively (p = 0.006). Permanent pacemaker implantation was required in four patients after SP valve replacement, but in only one patient after EP valve replacement (p = 0.326). The mean transprosthetic peak and mean gradients were 24.8 +/- 5.2 mmHg and 13.3 +/- 3.3 mmHg, respectively, in the SP group, and 19.0 +/- 6.5 mmHg and 10.4 +/- 3.0 mmHg, respectively, in the EP group (p = 0.024 and p = 0.087). The mean valve size was 23.8 +/- 1.3 mm and 23.3 +/- 1.5 mm in the SP and EP groups, respectively. The fall in platelet count after SP valve replacement was 180.4 +/- 79.4 x 10(3)/mu l on the first postoperative day (POD), and 114.1 +/- 51.2 x 10(3)/mu l with a minimum of 42 x 10(3)/mu l and a maximum of 230 x 10(3)/mu l at the nadir on POD 2.6 +/- 4.0. The mean minimum values at the nadir corresponded to 40% of the initial preoperative value. Conclusion: The sutureless SP bioprosthesis seems to represent a good alternative to conventional stented bioprostheses, especially in older patients with a high-risk profile, and particularly if concomitant surgical procedures are planned

Central Vascular Complications Following Elective Catheterization Using Transradial Percutaneous Coronary Intervention

Percutaneous coronary intervention is commonly used to treat coronary artery disease. Both transradial and transfemoral approaches are applied. In general, fewer complications are seen with the transradial approach compared to the transfemoral access, for which reason the transradial catheterization is frequently preferred. In this case presentation, we describe 2 cases of elective transradial coronary angiography both resulting in severe central vascular complications: perforation of the right subclavian artery with a mediastinal hematoma and dissection of the brachio- cephalic trunk and the aortic arch. Although the transradial access is generally considered safe, severe complications such as artery dissection or perforation can occur even in cases of elective procedures

Constrictive pericarditis with a life-threatening giant pericardial cyst and pectus excavatum as unusual cause for malign cardiac arrhythmias

Pericardial cysts are rare, abnormal, benign and usually congenital anomalies with an estimated incidence of 1:100.000 and are caused by an incomplete coalescence of foetal lacunae of pericardium development. The size of pericardial cysts varies from 1 to 5 cm and generally do not cause any symptoms. Pectus excavatum is one of the most frequent chest wall abnormalities with a caved-in appearance of the chest and mostly of unknown pathogenesis. We present a rare case of constrictive pericarditis with a huge pericardial cyst (11.6 x 8.7 x 7.1 cm) and pectus excavatum which led to compression of the heart and life-threatening cardiac arrhythmias