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Heart transplant (HTX) recipients are prone to develop serious symptoms after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and their vaccination is often ineffective. In this high-volume single center study, we aimed to examine the seroconversion rates achieved with various types and doses of SARS-CoV-2 vaccines and assessed factors influencing vaccine immunogenicity and predictors of severe SARS-CoV-2 infection. 229 HTX recipients were enrolled at a university clinic. Type of the first two doses of vaccine included mRNA, vector and inactivated vaccines as well. We carried out analyses on seroconversion after the second and third doses of vaccination and on severity of coronavirus disease 2019 (COVID-19). Anti-SARS-CoV-2 IgG levels were measured with Elecsys immunoassay (Roche). Effect of the first two vaccine doses was studied on patients who did not suffer SARS-CoV-2 infection before antibody measurement (n=175). Seroconversion after the third vaccine was analysed among seronegative patients after two doses (n=53). Predictors for severe infection defined as pneumonia, hospitalization or death was assessed in all HTX recipients who had COVID-19 (n=92). Logistic regression was applied for further analyses. 62% of the recipients became seropositive after the second vaccination. Longer time between HTX and vaccination (OR: 2.35, 95% CI: 1.28 - 4.49, p=0.007) and mRNA type of vaccine (OR: 4.83, 95% CI: 1.33 - 17.5, p=0.012) were predictors of seroconversion. 58% of the non-responsive patients became seropositive after receiving the third vaccine. Male sex increased the chance of IgG production after the third dose (OR: 5.65, 95% CI: 1.61 - 22.7, p=0.009). Clinical course of SARS-CoV-2 infection was severe in 32%. Of all parameters assessed, only seropositivity was proven to have a protective effect against severe infection (OR: 0.12, 95% CI: 0.02 - 0.64, p=0.019). Longer time since HTX, mRNA vaccine type and male sex promoted seroconversion after SARS-CoV-2 vaccination in HTX recipients. Seropositivity was proven to be protective against severe SARS-CoV-2 infection in single center cohort. Routine screening of HTX patients for anti-SARS-COV-2 antibodies may help to identify patients at risk for severe infection requiring addtional measures of anti-SARS-CoV-2 protection. [ABSTRACT FROM AUTHOR]

The existence of small bond angles (like those of triangles and squares) in amorphous silicon networks were studied by the tight-binding molecular dynamics method, by analyzing the statistical data of Si–Si–Si fragments inside large molecules, and also by the Reverse Monte-Carlo simulation method. The influence of small bond angles on the electronic density of states was revealed. [Copyright &y& Elsevier]

The growth of amorphous carbon (a-C) thin film on a [1 1 1] diamond surface has been studied by a tight-binding (TB) molecular dynamics (MD) technique. Six different three-dimensional networks were constructed with periodic boundary conditions in two dimensions. Time-dependent non-equilibrium growth was simulated with atom-by-atom deposition and it was described as in real experiments without an artificial model of energy dissipation. An additional seventh structure was constructed by a melt quenching procedure which is widely used in computer generations of amorphous networks. The final structures consist of over 100 atoms. Densities, radial distribution functions (RDFs), coordination numbers, bond angle distributions and ring statistics were analyzed. During relaxation the temperature in the amorphous film decreases with stretched-exponential function. The time dependence of bond length and bond angle deviations were also investigated. [Copyright &y& Elsevier]

We present the results of the first molecular dynamics simulations under realistic conditions pertinent to the incubation period of the bias enhanced nucleation process of diamond, based on the experimentally obtained average energies of CH3 and C2H2, at different bias voltages. It was found that the energies measured at a bias where the nucleation enhancement sets in are critical for the subplantation of both types of ions. In the case of the typically applied bias voltages, acetylene plays the dominant role. The molecule breaks up and the average final penetration depth of the carbon atoms is ∼5 A˚. The bombardment causes a significant increase of the mass density and the sp3 content in the range 4–8 A˚ below the surface despite the elevated temperature. The depth obtained for the main structural changes agrees well with the width of the amorphous carbon layer observed at the end of the incubation period for epitaxial nucleation. [Copyright &y& Elsevier]

Mycotic pseudoaneurysm of the ascending aorta is a potentially fatal complication after heart transplantation (HTx). Pseudomonas (P.) aeruginosa as a pathogen is mainly seen in immunosuppressed patients. Possible symptoms are malaise, chest or thoracic back pain, dyspnea, dysphagia or fever. Occasionally asymptomatic cases are also reported. There is often a previous mediastinitis or other infection in the patient history. In our patient a P. aeruginosa pseudoaneurysm developed after HTx without any alarm symptoms. The 67-year-old male patient treated with hypertension, diabetes mellitus and chronic renal failure attended a regular visit five months after HTx. He was asymptomatic except of an unexplainable weight loss. Lab test showed a moderate C-reactive protein level elevation over the course of two months (4-7-24-57 mg/L), therefore further examinations were prepared to identify the source of infection. Transthoracic echocardiography, chest X-ray, abdominal ultrasound and urine culture revealed no abnormalities. Chest computed tomography (CT) however showed a significant (90 mm) saccular dilatation of the tubular portion of ascending aorta. No obvious concomitant infection was reported. An urgent surgical intervention was indicated. A pseudoaneurysm was identified intraoperatively starting at the aortic anastomotic suture line, it was successfully resected and the sinotubular junction was reconstructed with a vascular prosthesis. Cultures of the resected specimen grew P. aeruginosa while all blood cultures taken pre- and postoperatively remained negative. Histological examinations verified aortitis. The patient received 3 weeks of intravenous treatment with ceftazidim followed by long-term oral ciprofloxacin. 19 day postoperative CT revealed no sign of recurrent graft infection. 4 months after the operation the patient was asymptomatic with controlled blood pressure and normal inflammatory markers. This case demonstrates the importance of considering a mycotic pseudoaneurysm of the aorta in the etiology of unexplainable inflammation following HTx. P. aeruginosa can be a causative organism which may indicate a long-term antibiotic therapy. It is important to check regularly the physical status, blood pressure, aortic diameters and inflammatory markers of the patient, as well as the potential side effects of antibiotic treatment. [ABSTRACT FROM AUTHOR]

Abstract: The microscopic processes in amorphous selenium caused by light-illumination have been investigated using molecular dynamics simulation. After photon absorption we treated the excited electron and hole independently. We found covalent bond breaking in amorphous networks with photo-induced excited electrons, whereas excited holes contribute to the formation of inter-chain bonds. We also observed a correlated macroscopic volume change of the amorphous sample. The interplay between photo-induced bond breaking and inter-chain bond formation leads to either volume expansion or shrinkage. Our results provide a new and universal description, which can explain simultaneously the photo-induced volume expansion and shrinkage. In the non-ideal case, a part of the microscopic processes is metastable and the total expansion includes the transient and metastable changes. We can describe this macroscopic effect, too. Our rate-equation models for a-Se and a-AsSe are supported by the results of recent measurements carried out by Y. Ikeda and K. Shimakawa. [Copyright &y& Elsevier]

Abstract: We have investigated in chalcogenide glasses the microscopic processes caused by illumination using tight-binding molecular dynamics computer simulation. After photon absorption we treated the excited electron and hole independently. We found covalent bond breaking in amorphous networks with photo-induced excited electrons, whereas excited holes contribute to the formation of inter-chain bonds. We also observed a correlated macroscopic volume change of the amorphous sample. Our results provide a new and universal description, which can explain simultaneously the photo-induced volume expansion and shrinkage. This model is supported by the results of recent measurements. [Copyright &y& Elsevier]

Cardiac allograft vasculopathy (CAV) is a poorly understood, accelerated form of coronary artery (CA) disease after heart transplantation (HTx). It has been proposed that CA vasculitis is part of CAV continuum or extension of HTx rejection. A 60-year-old male patient with metabolic syndrome and obstructive sleep apnea underwent HTx for dilated cardiomyopathy in 1998. The follow-up for 20 years was uneventful without rejection episode or severe CA disease on surveillance coronary CTA (CCTA). Maintenance immunosuppression consisted of cyclosporine and mycophenolate-mofetil. The patient had been complaining of dyspnea and fatigue since 2018. In November 2020, CCTA revealed novel perivascular adipose tissue (PAT) infiltration surrounding the CAs and ascending aorta raising suspicion of vasculitis which was confirmed by cardiac MRI. Autoimmune panel was negative and systemic vasculitis was excluded. In May 2021, significant increase in PAT infiltration was observed along with multiple severe stenoses of distal left anterior descending (LAD) CA on CCTA. PET-CT did not verify active vasculitis. Echocardiography revealed restrictive cardiac physiology. In November 2021, cardiac MRI confirmed active constrictive pericarditis (CP). Neither infiltrative, nor storage disease was verified. Besides elevated NT-proBNP and CRP levels, tests for infectious diseases and cancer were negative. High level of complement fixing donor-specific HLA class II antibodies (DSA; DQ2, DQ7) could have been detected since 2018. Considering the active CP and PAT infiltration, prednisolone was added; accordingly, patient reported relief of fatigue and dyspnea. As coronary angiography revealed severe stenoses of middle and distal LAD regions besides diffuse CAV, coronary stent implantation was performed. Patient died of fungal pneumonia in April 2022. Necropsy revealed remission of CP. Patient had been transplanted 23 years earlier, making this the longest interval for development of HTx vasculitis that has been reported. We hypothesize that CP could be late manifestation of chronic active antibody-mediated rejection with presence of high-titre DSAs and class II (DQ) DSAs associated with CAV. We postulate the active role of epicardial fat both in the development of CA disease and CP as a result of its inflammatory properties. [ABSTRACT FROM AUTHOR]

Although cardiac allograft vasculopathy (CAV) remains one of the leading causes of graft failure after heart transplantation (HTx), simultaneous thrombosis of multiple epicardial coronary arteries (CA) is an uncommon finding. A 43-year-old male patient with non-ischemic dilated cardiomyopathy underwent successful HTx in 2019. The first two years after HTx were uneventful, surveillance endomyocardial biopsies (EMB) did not reveal any rejection episodes, coronary CTA revealed only minimal non-calcified CA plaques. The patient was admitted to hospital due to fever and chest pain in 2021. Immunosuppressive therapy consisted of tacrolimus, mycophenolate-mofetil and methylprednisolone. ECG verified sinus rhythm. Laboratory test revealed elevated hsTroponin T, NT-proBNP and CRP levels. Cytomegalovirus, SARS-CoV-2-virus and hemoculture testing was negative. Several high-titre donor-specific HLA class I and II antibodies (DSAs; including complement-binding DQ7) could have been detected since 2020. Echocardiography confirmed mildly decreased left ventricular systolic function and apical hypokinesis. EMB verified mild cellular and antibody-mediated rejection (ABMR) according to ISHLT grading criteria. Cardiac MRI revealed inferobasal and apical myocardial infarction (MI); thus, an urgent coronary angiography was performed. This confirmed thrombotic occlusions in all three main epicardial CAs and in first diagonal CA. As revascularization was not feasible, antithrombotic therapy with acetylsalicylic acid, clopidogrel and enoxaparin was started for secondary prevention. Tests for immune system disorders, thrombophilia and cancer were negative. Patient suddenly died ten days after admission. Necropsy revealed intimal proliferation in all three main epicardial CAs, endothelitis, thrombosis, chronic pericoronary fat inflammation, fat necrosis, and subacute MI. CA vasculitis owing to persistent high-titre DSAs, chronic ABMR and acute cellular and antibody-mediated rejection led to multivessel CA thrombosis and acute multiple MI. ABMR after HTx may be underdiagnosed with traditional pathological methods. Pathologies affecting coronary vasculature of HTx patients with DSAs, unique manifestations of CAV lesions and occlusive thrombosis of non-stenotic, non-atherosclerotic lesions should be emphasized. [ABSTRACT FROM AUTHOR]

Abstract: In the proposed contribution the effect of the shear correction function is originally studied and evaluated in modal analysis of the functionally graded material (FGM) beams. Spatially continuous variations of the material properties are considered. The shear correction function is calculated from the shear strain energy equation including spatial Poisson′s ratio variations. The equations of the homogenized FGM beam free vibration and their solution is presented including the shear correction function. Four coupled differential equations are derived and used in the modal analysis of beams with polynomial continuous longitudinal and transversal variations of material properties. Further, 2nd order beam effects and longitudinal varying elastic beam foundations are considered. The influence of using an average shear correction factor is evaluated through numerical experiments. Additionally, the longitudinal eigenfrequencies are calculated. Continuum solutions using solid finite elements are taken as a reference for comparison purposes. [Copyright &y& Elsevier]