Formation of GeO2 under Graphene on Ge(001)/Si(001) Substrates Using Water Vapor.

The problem of graphene protection of Ge surfaces against oxidation is investigated. Raman, X-Ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements of graphene epitaxially grown on Ge(001)/Si(001) substrates are presented. It is shown that the penetration of water vapor through graphene defects on Gr/Ge(001)/Si(001) samples leads to the oxidation of germanium, forming GeO2. The presence of trigonal GeO2 under graphene was identified by Raman and XRD measurements. The oxidation of Ge leads to the formation of blisters under the graphene layer. It is suggested that oxidation of Ge is connected with the dissociation of water molecules and penetration of OH molecules or O to the Ge surface. It has also been found that the formation of blisters of GeO2 leads to a dramatic increase in the intensity of the graphene Raman spectrum. The increase in the Raman signal intensity is most likely due to the screening of graphene by GeO2 from the Ge(001) surface.

Risk factors for permanent pacemaker implantation in patients receiving a balloon-expandable transcatheter aortic valve prosthesis.

Permanent pacemaker implantation (PPI) is a widely recognized complication associated with TAVI (incidence up to 20%). Smaller registries have identified several variables associated with PPI. The objective was to validate patient- and transcatheter aortic valve implantation (TAVI)-related procedural variables associated with PPI. We performed a retrospective analysis of patients from six European centers undergoing TAVI with the Edwards SAPIEN 3 prosthesis. Baseline variables and pre-procedural ECG characteristics and CT-scans were taken into account. Data for 1745 patients were collected; 191 (10.9%) required PPI after TAVI. The baseline variables pulmonary hypertension (OR 1.64; 95% CI 1.01-2.59), QRS duration > 117 ms (OR 2.58; 95% CI 1.73-3.84), right bundle branch block (RBBB; OR 5.14; 95% CI 3.39-7.72), left anterior hemi block (OR 1.92; 95% CI 1.19-3.02) and first-degree atrioventricular block (AVB, OR 1.63; 95%CI 1.05-2.46) were significantly associated with PPI. RBBB (OR 8.11; 95% CI 3.19-21.86) and first-degree AVB (OR 2.39; 95% CI 1.18-4.66) remained significantly associated in a multivariate analysis. Procedure-related variables included access site (TF; OR 1.97; 95% CI 1.07-4.05), implanted valve size (29 mm; OR 1.88; 95% CI 1.35-2.59), mean TAVI valve implantation depth below the annulus > 30% (OR 3.75; 95% CI 2.01-6.98). Patients receiving PPI had longer ICU stays and later discharges. Acute kidney injury stage 2/3 was more common in patients with PPI until discharge (15.2 vs. 3.1%; p = 0.007), but was not statistically significant thereafter. Further differences in outcomes at 30 days did not reach significance. The data will aid pre- and post-procedural patient management and prevent adverse long-term outcomes.Clinical Trial: NCT03497611.

Destructive role of oxygen in growth of molybdenum disulfide determined by secondary ion mass spectrometry.

The application of secondary ion mass spectrometry (SIMS) in investigation and comparison of molybdenum disulfide (MoS2) films grown on SiO2, Al2O3 and BN substrates is presented. SIMS measurements of the MoS2/substrate interface reveals oxygen out-diffusion from the substrates containing oxygen and the formation of an amorphous MoOS layer in addition to MoS2. The total area of MoS2 domains covering the substrate is directly related to the type of substrate. For SiO2, small triangular domains of MoS2 separated by amorphous MoOS material are observed. For Al2O3, the sizes of the MoS2 domains are drastically improved due to the higher stability of sapphire. For a BN substrate, SIMS measurements reveal a uniform MoS2 coverage over the whole 2-inch wafer. These results show the destructive role of oxygen released from substrates such as SiO2 or Al2O3 during the growth process of MoS2. The fast and cheap growth process on a non-oxide substrate allows large wafer-scale uniform molybdenum disulfide material to be obtained, which is promising for device fabrication.

Growth of highly oriented MoS2via an intercalation process in the graphene/SiC(0001) system.

A method of growing highly oriented MoS2 is presented. First, a Mo film is deposited on a graphene/SiC(0001) substrate and the subsequent annealing of it at 750 °C leads to intercalation of Mo underneath the graphene layer, which is confirmed by secondary ion mass spectrometry (SIMS) measurements. Formation of highly oriented MoS2 layers is then achieved by sulfurization of the graphene/Mo/SiC system using H2S gas. X-ray diffraction reveals that the MoS2 layers are highly oriented and parallel to the underlying SiC substrate surface. Further SIMS experiments reveal that the intercalation process occurs via the atomic step edges of SiC and Mo and S atoms gradually diffuse along SiC atomic terraces leading to the creation of the MoS2 layer. This observation can be explained by a mechanism of highly oriented growth of MoS2: nucleation of the crystalline MoS2 phase occurs underneath the graphene planes covering the flat parts of SiC steps and Mo and S atoms create crystallization fronts moving along terraces.

Surgical management of outflow tract obstruction after transapical mitral valve implantation.

Left ventricular outflow tract (LVOT) obstruction due to systolic anterior motion of the anterior mitral valve leaflet (AML) is a known complication after mitral valve repair or transfemoral/transapical mitral valve implantation (TMVI). We present a patient with a previous mitral valve repair who developed LVOT obstruction after TMVI in whom the AML was surgically resected using a transaortic approach.

Modifiable risk factors for permanent pacemaker after transcatheter aortic valve implantation: CONDUCT registry.

OBJECTIVE: The onset of new conduction abnormalities requiring permanent pacemaker implantation (PPI) after transcatheter aortic valve implantation (TAVI) is still a relevant adverse event. The main objective of this registry was to identify modifiable procedural risk factors for an improved outcome (lower rate of PPI) after TAVI in patients at high risk of PPI. METHODS: Patients from four European centres receiving a balloon-expandable TAVI (Edwards SAPIEN 3/3 Ultra) and considered at high risk of PPI (pre-existing conduction disturbance, heavily calcified left ventricular outflow tract or short membranous septum) were prospectively enrolled into registry. RESULTS: A total of 300 patients were included: 42 (14.0%) required PPI after TAVI and 258 (86.0%) did not. Patients with PPI had a longer intensive care unit plus intermediate care stay (65.7 vs 16.3 hours, p<0.001), general ward care stay (6.9 vs 5.3 days, p=0.004) and later discharge (8.6 vs 5.0 days, p<0.001). Of the baseline variables, only pre-existing right bundle branch block at baseline (OR 6.8, 95% CI 2.5 to 18.1) was significantly associated with PPI in the multivariable analysis. Among procedure-related variables, oversizing had the highest impact on the rate of PPI: higher than manufacturer-recommended sizing, mean area oversizing as well as the use of the 29 mm valve (OR 3.4, 95% CI 1.4 to 8.5, p=0.008) all were significantly associated with PPI. Rates were higher with the SAPIEN 3 (16.1%) vs SAPIEN 3 Ultra (8.5%), although not statistically significant but potentially associated with valve sizing. Implantation depth and postdelivery balloon dilatation also tended to affect PPI rates but without a statistical significance. CONCLUSION: Valve oversizing is a strong procedure-related risk factor for PPI following TAVI. The clinical impact of the valve type (SAPIEN 3), implantation depth, and postdelivery balloon dilatation did not reach significance and may reflect already refined procedures in the participating centres, giving attention to these avoidable risk factors. TRIAL REGISTRATION NUMBER: NCT03497611.

Echo-guided presentation of the aortic valve minimises contrast exposure in transcatheter valve recipients.

OBJECTIVES: We have developed a method using transthoracic echocardiography in establishing optimal visualization of the aortic root, to reduce the amount of contrast medium used in each patient. BACKGROUND: During transcatheter aortic valve implantation, it is necessary to obtain an optimal fluoroscopic projection for deployment of the valve showing the aortic ostium with the three cusps aligned in the beam direction. This may require repeat aortic root angiograms at this stage of the procedure with a high amount of contrast medium with a risk of detrimental influence on renal function. METHODS: We studied the conventional way and an echo guided way to optimize visualisation of the aortic root. Echocardiography was used initially allowing easier alignment of the image intensifier with the transducer's direction. RESULTS: Contrast volumes, radiation/fluoroscopy exposure times, and postoperative creatinine levels were significantly less in patients having the echo-guided orientation of the optimal fluoroscopic angles compared with patients treated with the conventional approach. CONCLUSION: We present a user-friendly echo-guided method to facilitate fluoroscopy adjustment during transcatheter aortic valve implantation. In our series, the amounts of contrast medium and radiation have been significantly reduced, with a concomitant reduction in detrimental effects on renal function in the early postoperative phase.

Non-Bacterial Thrombotic Endocarditis: A Presentation of COVID-19.

The SARS-CoV-2 virus is a newly emergent pathogen first identified in Wuhan, China, and responsible for the COVID-19 global pandemic. In this case report we describe a manifestation of non-bacterial thrombotic endocarditis with continuous peripheral embolization in a COVID-19-positive patient. The patient responded well to high-dose LMWH treatment with cessation of the embolic process. LEARNING POINTS: Raising awareness of possible complications of COVID-19.To highlight the importance of the careful consideration of and dosage of anticoagulation in non-bacterial thrombotic endocarditis.

Minimizing the risk for left ventricular rupture during transcatheter aortic valve implantation by reducing the presence of stiff guidewires in the ventricle.

OBJECTIVES: The presence of a stiff guidewire in the apex of the left ventricle (LV) is a known risk factor for LV perforation. Our goal was to minimize the risk of LV rupture during transcatheter aortic valve implantation (TAVI) by omitting the interaction between the stiff guidewire and the LV apex using a modified procedure. METHODS: A TAVI protocol designed to allow minimal interaction between a stiff guidewire and the LV was developed in Linköping University Hospital in Sweden. A total of 316 patients were treated exclusively by this approach between March 2014 and May 2018. RESULTS: All procedures were completed successfully. There were no cases (0%) of ventricular perforation. Only 1 patient (0.3%) had a pericardial effusion, and it was due to annulus rupture. There was 1 case of acute kidney injury (0.3%). Five patients (1.6%) required a new permanent pacemaker. Stroke occurred in 3 patients (0.9%). No patient had valve embolization. Vascular complications were experienced by 6 patients (1.9%). A mild paravalvular leak occurred in 27 (8.5%) patients. At 30 days post-TAVI, 6 patients (2%) had died. The mortality rate at 1 year was 8.6% (n = 20/232). CONCLUSIONS: Our series shows that TAVI without the prolonged use of a stiff guidewire in the LV apex is feasible. The risk of LV perforation is eliminated by this approach, and other procedural complications are limited.

Determination of selected drugs in human urine by differential pulse voltammetry technique.

A new, simple and selective differential pulse voltammetry (DPV) method for the simultaneous determination of selected drugs in model solutions and spiked human urine samples with prior extraction was developed and validated. The objects of analysis were paracetamol, furosemide, dipyrone, cefazolin and dexamethasone belonging to four different therapeutic groups (antibiotics, analgesic, demulcent and diuretic). Analytical methods for the preparation of urine samples for voltammetric analysis (liquid-liquid extraction--LLE and solid-phase extraction--SPE) were worked out and optimized. Hanging mercury drop electrode (HMDE) and graphite electrode were used as working electrodes. Reference electrode was Ag|AgCl|KCl((sat.)), whereas auxiliary electrode--platinum electrode. The optimal conditions for quantitative determination were obtained in a Britton-Robinson (BR) buffer at pH 2.4. Quantification was performed by means of calibration curve and standard addition methods. The calibration curves of analysed drugs are linear within the range of concentration: 6.61-66.10, 6.05-54.42, 6.00-65.00, 4.20-33.58 and 0.51-3.06 microM for paracetamol, furosemide, dipyrone, cefazolin and dexamethasone, respectively. The levels of analysed compounds in human urine can be successfully determined using this developed method with no matrix effect.

Percutaneous closure of recanalised ductus arteriosus--a single-centre experience.

INTRODUCTION: Restoration of blood flow through a previously occluded ductus arteriosus may occur in some patients. Treatment strategy in patients with such residual shunts has not yet been uniformly established. AIM: To present single-centre experience and to attempt to establish a strategy of management of patients with residual ductus arteriosus shunts following percutaneous closure. METHODS: Of 352 patients who underwent percutaneous closure of ductus arteriosus, in 13 subjects complete closure failed (coils and Rashkind occluders were used in 10 and 3 patients, respectively). In these patients other percutaneous interventions aiming at total closure of residual shunt were attempted. RESULTS: In 12 patients coils were inserted (one patient received two coils). Introduction of implant in one patient failed, but total occlusion of the shunt was confirmed one day after the procedure. Trivial residual shunt was observed in one patient after one-year follow-up. CONCLUSIONS: Percutaneous treatment of residual shunts within the ductus arteriosus is an effective and safe procedure. In our opinion identifying and treating such leaks is important, as it prevents complications and long-term need for antibiotic prevention of infective endocarditis. In the case of a small residual shunt, insertion of a coil seems to be the optimal therapy due to the low cost of the device, favourable design and high effectiveness. For patients in whom anatomy of the ductus arteriosus has been significantly changed, particularly in previously treated subjects, techniques using vascular loops or insertion using a catheter wedge may be helpful.

Left Atrial Pressure Monitoring With an Implantable Wireless Pressure Sensor After Implantation of a Left Ventricular Assist Device.

After implantation of a continuous-flow left ventricular assist device (LVAD), left atrial pressure (LAP) monitoring allows for the precise management of intravascular volume, inotropic therapy, and pump speed. In this case series of 4 LVAD recipients, we report the first clinical use of this wireless pressure sensor for the long-term monitoring of LAP during LVAD support. A wireless microelectromechanical system pressure sensor (Titan, ISS Inc., Ypsilanti, MI) was placed in the left atrium in four patients at the time of LVAD implantation. Titan sensor LAP was measured in all four patients on the intensive care unit and in three patients at home. Ramped speed tests were performed using LAP and echocardiography in three patients. The left ventricular end-diastolic diameter (cm), flow (L/min), power consumption (W), and blood pressure (mm Hg) were measured at each step. Measurements were performed over 36, 84, 137, and 180 days, respectively. The three discharged patients had equipment at home and were able to perform daily recordings. There were significant correlations between sensor pressure and pump speed, LV and LA size and pulmonary capillary wedge pressure, respectively (r = 0.92-0.99, p < 0.05). There was no device failure, and there were no adverse consequences of its use.

Endovascular Stenting of a LVAD Outflow Graft Thrombosis.

We report the endovascular stenting of an outflow tract thrombosis in a left ventricular assist device in a patient with relative contraindications to sternotomy and pump exchange. This report highlights the importance of simultaneous prevention of stroke using filter devices in the common carotid arteries.

Highly selective covalent organic functionalization of epitaxial graphene.

Graphene functionalization with organics is expected to be an important step for the development of graphene-based materials with tailored electronic properties. However, its high chemical inertness makes difficult a controlled and selective covalent functionalization, and most of the works performed up to the date report electrostatic molecular adsorption or unruly functionalization. We show hereafter a mechanism for promoting highly specific covalent bonding of any amino-terminated molecule and a description of the operating processes. We show, by different experimental techniques and theoretical methods, that the excess of charge at carbon dangling-bonds formed on single-atomic vacancies at the graphene surface induces enhanced reactivity towards a selective oxidation of the amino group and subsequent integration of the nitrogen within the graphene network. Remarkably, functionalized surfaces retain the electronic properties of pristine graphene. This study opens the door for development of graphene-based interfaces, as nano-bio-hybrid composites, fabrication of dielectrics, plasmonics or spintronics.

Salting-out assisted extraction method coupled with hydrophilic interaction liquid chromatography for determination of selected ß-blockers and their metabolites in human urine.

In this study, a new analytical method was developed and validated for the simultaneous analysis of ß-blockers (metoprolol, propranolol, carvedilol) and their metabolites (5'-hydroxycarvedilol, O-desmethylcarvedilol, α-hydroxymetoprolol, O-desmethylmetoprolol, 5-hydroxypropranolol) in human urine. A salting-out assisted liquid-liquid extraction (SALLE) procedure was used for sample preparation. Several parameters affecting the extraction efficiency and method sensitivity including the type and volume of the extraction solvent, the type and quantity of the inorganic salt, extraction time and sample pH were investigated. Hydrophilic interaction liquid chromatography-ultraviolet detection (HILIC-UV) was used for the determination of all analytes. During method development, the effects of mobile phase components (type, pH, concentration of salt, organic modifier type and content, flow rate, column temperature) on the retention and separation of ß-blockers and metabolites on the five different HILIC columns were examined. The method was linear for concentrations ranging from 0.1 to 8.0µg/mL, with determination coefficients higher than 0.993 for all analytes. The limits of quantification were in the range from 0.1 to 0.2µg/mL. Intra- and inter-day precision ranged from 0.1 to 8.9%, and accuracy was within±13% interval for all analytes. Under the optimized conditions, extraction efficiency was greater than 83.4% for determined compounds. The validated method was then applied to the measurement of ß-blockers and their metabolites in human urine samples.

Can predilatation in transcatheter aortic valve implantation be omitted? - a prospective randomized study.

BACKGROUND: The use of a balloon expandable stent valve includes balloon predilatation of the aortic stenosis before valve deployment. The aim of the study was to see whether or not balloon predilatation is necessary in transcatheter aortic valve replacement (TAVI). METHODS: Sixty consecutive TAVI patients were randomized to the standard procedure or to a protocol where balloon predilatation was omitted. RESULTS: There were no significant differences between the groups regarding early hemodynamic results or complication rates. CONCLUSIONS: TAVI can be performed safely without balloon predilatation and with the same early results as achieved with the standard procedure including balloon predilatation. The reduction in the number of pacing periods required may be beneficial for the patient.

Transvenous Implantation of a Stent Valve in Patients With Degenerated Mitral Prostheses and Native Mitral Stenosis.

BACKGROUND: The purpose of this study was to report the use of a transvenous transseptal approach using a stent valve in patients with degenerated biological mitral valve prostheses, regurgitation after mitral repair, and native mitral stenosis. METHODS: Ten patients (median age, 74 years; range, 20-89 years; 5 men and 5 women) with degenerated mitral bioprosthetic valves (n = 7), failed mitral repair (n = 1), or calcified native stenotic valves (n = 2) underwent transvenous implantation of a stent valve. RESULTS: The procedure was initially successful in all patients. Predilation was performed for balloon sizing only in the 2 patients with native mitral stenosis. The stent valve was deployed during 1 period of rapid pacing. A guidewire, as a loop from the right femoral vein and through the left ventricular apex, facilitated a good angle and secure positioning of the stent valve. An ultrasonographically guided puncture of the apex was carried out in 6 patients, and in the other 4 we performed a minithoracotomy before apical puncture. All valves were implanted in a good position with improved function and without significant paravalvular leakage (PVL). There were no periprocedural deaths. The 30-day survival was 80% (8 of 10 patients), and 60% (6 of 10) of patients were still alive a median time of 290 days after the procedure. CONCLUSIONS: Transvenous transseptal implantation of a stent valve was performed in 10 patients with mitral valve disease, with good early functional results. These high-risk patients must be carefully selected by a multidisciplinary team because the procedure carries a high mortality.

Graphene growth on Ge(100)/Si(100) substrates by CVD method.

The successful integration of graphene into microelectronic devices is strongly dependent on the availability of direct deposition processes, which can provide uniform, large area and high quality graphene on nonmetallic substrates. As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm(-1).

Efficacy and safety of the Lotus Valve System for treatment of patients with severe aortic valve stenosis and intermediate surgical risk: Results from the Nordic Lotus-TAVR registry.

BACKGROUND: Transcatheter aortic valve replacement (TAVR) has become an established therapeutic option for patients with symptomatic, severe aortic valve stenosis (AS) who are ineligible or at high risk for conventional valvular surgery. In Northwestern Europe, the TAVR technology is also increasingly used to treat patients with an intermediate risk profile. METHODS AND RESULTS: The study was designed as an independent Nordic multicenter registry of intermediate risk patients treated with the Lotus Valve System (Boston Scientific, MA, USA; N=154). Valve Academic Research Consortium (VARC)-defined device success was obtained in 97.4%. A Lotus Valve was successfully implanted in all patients. There was no valve migration, embolization, ectopic valve deployment, or TAV-in-TAV deployment. The VARC-defined combined safety rate at 30days was 92.2%, with a mortality rate of 1.9% and stroke rate of 3.2%. The clinical efficacy rate after 30days was 91.6% - only one patient had moderate aortic regurgitation. When considering only those patients in the late experience group (N=79), the combined safety and clinical efficacy rates were 93.7% and 92.4%, respectively. The pacemaker implantation rate was 27.9% - this rate was 12.8% in case of a combined implantation depth <4mm and a device/annulus ratio<1.05. CONCLUSIONS: The present study demonstrates the efficacy and safety of the repositionable, retrievable Lotus Valve System in intermediate risk patients with AS. The VARC-defined device success rate was 97.4% with a 30-day patient safety and clinical efficacy rate of more than 90%. Less than moderate aortic regurgitation was obtained in 99.4% of patients.

Iatrogenic cardiac arrhythmias following transcatheter or surgical closure of atrial septal defect in children.

BACKGROUND: Invasive procedures involving the atria may promote the development of iatrogenic cardiac arrhythmias. AIM: To analyse the prevalence of cardiac arrhythmias following transcatheter or cardiosurgical closure of the secundum type atrial septal defect (ASD). METHODS: The study group consisted of 91 patients, aged 2-18 years with haemodynamically significant ASD who underwent surgical (n=44) or transcatheter (Amplatzer occluder) (n=47) closure of ASD. Standard ECG and Holter ECG recordings, obtained before and after the procedure, were analysed. The follow-up duration ranged from 2.5 to 5.5 years. Cardiac arrhythmias were divided into benign or significant (requiring pharmacological therapy), early or late, and transient or permanent. RESULTS: Cardiac arrhythmias were detected in 16 (36%) patients who underwent surgery compared with 1 (2.1%) patient who underwent transcatheter ASD closure (p<0.05). In surgically treated patients, arrhythmias were benign in 9 patients, significant in 7 children, early in 15 subjects, late in one patient, transient in 13 children and permanent in 3 subjects. One patient, who underwent transcatheter ASD closure, developed paroxysmal supraventricular tachycardia one day after the procedure, successfully terminated with verapamil. CONCLUSIONS: Transcatheter closure of ASD is associated with a lower risk of procedure-related arrhythmias than surgical treatment. However, longer follow-up in patients treated with transcatheter procedure is needed in order to draw definite conclusions.