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A theoretical study was conducted to analyze electronic, elastic, and thermodynamic properties and the structural stability of the intermetallic materials Al3Ti1−xZrx for tetragonal-D022 and cubic-L12 structures carried out based on DFT. The findings indicate that the D022 phase has demonstrated more stability than the L12 phase and the possibility of a structural phase transition under pressure effect for concentrations x = 0.25 and x = 0.5. With increasing x concentration, the resulting lattice parameters drop. The density of states at the Fermi level, determines the electronic stability exhibited by these compounds. A pseudo-gap in proximity to the Fermi level implies the establishment of directional covalent bonding. The electronic structures support the phase stability results and show that the bonding in these compounds is more directed. Measurement techniques are employed to determine the number of bonding electrons per atom and the coefficient of electronic-specific heat. Both the mechanical as well as elastic properties of the considered alloys are examined. The findings demonstrate that all explored alloys are brittle, and D022 phase is stiffer than the L12 phase. The thermal characteristics are predicted via the quasi-harmonic Debye model. [ABSTRACT FROM AUTHOR]

The transition-metal free S-vinylation of thiophenols by vinylbenziodoxolones (VBX) constituted an important step forward in hypervalent iodine-mediated vinylations, highlighting the difference to vinyliodonium salts and that the reaction outcome was influenced by the substitution pattern of the benziodoxolone core. In this study, we report several new classes of hypervalent iodine vinylation reagents; vinylbenziodazolones, vinylbenziodoxolonimine and vinyliodoxathiole dioxides. Their synthesis, structural and electronic properties are described and correlated to the S-vinylation outcome, shedding light on some interesting facets of these reagents.

In this paper, the gyrotropic bi-anisotropy of the chiral medium in substrate constitutive parameters (ξc and ηc) of a rectangular microstrip patch antenna is introduced in order to observe its effects on the complex resonant frequency and half-power bandwidth. The analysis is based on the full-wave spectral domain approach using the Moment Method, with sinusoidal type basis functions. The numerical calculations related to the dominant mode have been carried out, and it has been observed that the resonant frequency and the bandwidth are directly linked to the medium chirality. The new results can be considered as a generalisation form of the previously published work. [ABSTRACT FROM AUTHOR]

Segmental contractile reserve measured by dobutamine magnetic resonance imaging quantitatively predicts improvement in end-systolic wall thickness after revascularization. Segments with end-systolic wall thickness <7 mm at rest do not demonstrate contractile reserve or improve after revascularization. [ABSTRACT FROM AUTHOR]

Determines if the use of nitroglycerin magnetic resonance imaging (MRI) predicts segmental recovery of function after revascularization and to compare the technique with dobutamine stress echocardiography. Absence of electrocardiographic changes before and after revascularization; Merits of using nitroglycerin MRI in assessing contractile reserve.

In this paper, we present an analytical study for the investigation of the effects of the magnetoelectric elements of a reciprocal and nonreciprocal bianisotropic grounded substrate on the input impedance, resonant length of a dipole antenna as well as on the mutual coupling between two element printed dipole array in three configuration geometries: broadside, collinear and echelon printed on the same material. This study examines also the effect of the considered bianisotropic medium on the electric and magnetic field distributions that has been less addressed in the literature for antenna structures. Computations are based on the numerical resolution, using the spectral method of moments, of the integral equation developed through the mathematical derivation of the appropriate spectral Green's functions of the studied dipole configuration. Original results, for chiral, achiral, Tellegen and general bi-anisotropic media cases, are obtained and discussed with the electric and magnetic field distributions for a better understanding and interpretation. These interesting results can serve as a stepping stone for further works to attract more attention to the reciprocal and non-reciprocal Tellgen media in-depth studies., (© 2022. The Author(s).)

Background: Carcinoid heart disease (CaHD) is a rare condition that has a high impact on the morbidity and mortality of its patients. Once heart failure symptoms develop in the patient with CaHD, cardiac valve surgery is often the only effective treatment. Although atrioventricular block (AVB) is a known postoperative complication of the valve surgery, the incidence of AVB in this population has not been well described., Methods: Comprehensive records were collected retrospectively on consecutive patients with CaHD who underwent a valve surgery at a tertiary medical center from January 2001 to December 2015. We excluded patients with pre-existing permanent pacemaker (PPM)., Results: Nineteen consecutive patients were included in this study and 18 of them underwent at least dual valve (tricuspid and pulmonary valve) replacement surgery. Our 30-day post-surgical mortality was 0%. During the 6-month observation period following the surgery, 31.5% (n = 6) required PPM implantation due to complete AVB. There was no statistical difference in baseline characteristics and electrocardiographic and echocardiographic parameters between the patients who did or did not require PPM placement., Conclusions: Our study revealed that almost one-third of CaHD patients who underwent a valve replacement surgery developed AVB requiring PPM implantation. Due to high incidence of PPM requirement, we believe that prophylactic placement of an epicardial lead during the valve surgery can be helpful in these patients to reduce serious complication from placement of pacemaker lead on a later date through a prosthetic valve., Competing Interests: All authors have nothing to disclose., (Copyright 2020, Sunjic et al.)

In clinical practice, reducing the burden of persistent atrial fibrillation by pharmacological means is challenging. We explored if blocking the background and the acetylcholine-activated inward rectifier potassium currents (I K1 and I KACh ) could be antiarrhythmic in persistent atrial fibrillation. We thus tested the hypothesis that blocking I K1 and I KACh with chloroquine decreases the burden of persistent atrial fibrillation. We used patch clamp to determine the IC 50 of I K1 and I KACh block by chloroquine and molecular modeling to simulate the interaction between chloroquine and Kir2.1 and Kir3.1, the molecular correlates of I K1 and I KACh . We then tested, as a proof of concept, if oral chloroquine administration to a patient with persistent atrial fibrillation can decrease the arrhythmia burden. We also simulated the effects of chloroquine in a 3D model of human atria with persistent atrial fibrillation. In patch clamp the IC 50 of I K1 block by chloroquine was similar to that of I KACh . A 14-day regimen of oral chloroquine significantly decreased the burden of persistent atrial fibrillation in a patient. Mathematical simulations of persistent atrial fibrillation in a 3D model of human atria suggested that chloroquine prolonged the action potential duration, leading to failure of reentrant excitation, and the subsequent termination of the arrhythmia. The combined block of I K1 and I KACh can be a targeted therapeutic strategy for persistent atrial fibrillation., (Copyright © 2019 Tobón, Palacio, Chidipi, Slough, Tran, Tran, Reiser, Lin, Herweg, Sayad, Saiz and Noujaim.)

We describe a patient diagnosed with a neuroendocrine tumor of the small intestine metastatic to the heart who underwent successful cardiac metastasectomy. The tumor was located on the right ventricle free wall, obstructing the right ventricular outflow tract. There was no valvular involvement., (Copyright © 2016 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

This report describes a patient who underwent cardiac resynchronization therapy (CRT) in the setting of a severe stenosis in the lateral coronary vein that prevented passage of a left ventricular lead. The stenosis was unresponsive to standard compliant balloon dilatation but was successfully treated with a noncompliant balloon. Venoplasty with noncompliant balloon should be considered for resistant coronary vein stenosis encountered during CRT device implantation.

Stentless mitral valves have found little clinical utility to date due to difficulty in insertion. A new design for a stentless mitral valve, a modification of an existing aortic stentless prosthesis, is described. The new design mimics the native mitral physiology, and its insertion is easier than with existing stentless mitral valves. Commercially available stentless aortic valves were inserted into 2 pigs. The valves were modified so that the commissural posts were restrained. The valves were partially recessed into the left ventricular cavity, secured to the annulus, and anchored to the native papillary muscles. Both pigs were weaned from bypass successfully, and both valves functioned normally with trace regurgitation noted on echocardiography. This design affords the benefit of the reapproximation of native physiology. Preservation of papillary-annular continuity should allow maximal left ventricular function. Lack of a stent should allow avoidance of long-term anticoagulation.

Percutaneous closure of a secundum atrial septal defect was performed successfully via the jugular approach in a 77-year-old patient with heparin-induced thrombocytopenia and total occlusion of the inferior vena cava using the Amplatzer septal occluder after an unsuccessful attempt using the CardioSEAL septal occluder. This case demonstrates the advantages of the jugular approach in the patient with difficult anatomy and the advantage of the Amplatzer over the CardioSEAL device in this situation., (Copyright 2004 Wiley-Liss, Inc.)

Percutaneous transvenous mitral commissurotomy was performed successfully via the transjugular approach in a patient with severe rheumatic mitral stenosis and obstruction of the inferior vena cava due to prior liver transplantation. This case demonstrates the advantage of the jugular approach in patients with difficult anatomy., (Copyright 2003 Wiley-Liss, Inc.)

This report describes the response of a Vitatron Diamond II DDDR pacemaker to atrial flutter in a patient who developed alternating duration of the ventricular paced cycles during automatic mode switching to the DDIR mode. This device activates mode switching on a beat-to-beat basis and exhibits "ventricular hysteresis" in the DDIR mode when an atrial sensed event is detected during the period corresponding with the AV delay prior to emission of the ventricular stimulus. Such unusual behavior must not be interpreted as pacemaker malfunction.

A 61-year-old woman presented to the emergency department after experiencing palpitations, shortness of breath, and syncope while taking a shower. Her husband revived her with mouth-to-mouth resuscitation. She had had a similar episode three days earlier while making her bed and had lost consciousness for about 10 sec. She did not appear to have had a seizure. Five months earlier, while taking a walk, she had experienced dizziness, dyspnea, and chest pressure lasting about an hour. A workup at that time included cardiac catheterization, lung scanning, and esophagogastroduodenoscopy, but no abnormality was found. Lower extremity edema was noted.

Objective: We recently provided evidence for contraction-induced attenuation of reflex sympathetic vasoconstriction in human skeletal muscle microcirculation. We now asked whether contraction-induced modulation of alpha-adrenoceptor mediated vasoconstriction in the human forearm (a) is evident in a large artery supplying the contracting skeletal muscle and (b) implicates a post-junctional site of action., Methods and Results: To address these questions in humans, we used phase-contrast magnetic resonance imaging to measure blood flow velocity and cross-sectional area of the brachial artery during brachial-artery infusion of the alpha-adrenoceptor agonist norepinephrine (NE) (1.1 g/min for 5 min) at rest and during mild ipsilateral rhythmic handgrip (20% of maximum). At rest, brachial artery conductance decreased progressively during the entire 5 min period of infusion (baseline to first half to second half of infusion: 0.421 +/- 0.157 to 0.255 +/- 0.187 to 0.012 +/- 0.014 ml/min/mmHg, P < 0.05). When NE was superimposed on handgrip, conductance at first decreased sharply (1.205 +/- 0.127 to 0.330 +/- 0.097 ml/min/mmHg, P < 0.05). However, during the second half of the infusion, conductance did not decrease further but rather returned progressively toward baseline (0.476 +/- 0.199 ml/min/mmHg at the end of the exercise, P < 0.05 vs. NE alone)., Conclusion: These data provide new evidence in humans that alpha-adrenoceptor mediated vasoconstriction is sensitive to modulation by skeletal muscle contraction. Such modulation is evident at the level of a large conduit artery and it involves a post-junctional mechanism of action.

MR imaging cardiac quantitation is accurate, highly reproducible, and feasible using equipment available in most hospitals. For determination of myocardial mass, evaluation of RV function, and quantitative measurements of flow in the great vessels and peripheral vasculature, MR imaging is the reference method. Availability of methods for rapid scanning and analysis will lead to increased use of cardiac MR imaging in quantifying cardiac function.

Background: The noninvasive measurement of absolute epicardial coronary arterial flow and flow reserve would be useful in the evaluation of patients with coronary circulatory disorders. Phase-contrast magnetic resonance imaging (PC-MRI) has been used to measure coronary arterial flow in animals, but its accuracy in humans is unknown., Methods and Results: Twelve subjects (7 men, 5 women: age 44 to 67 years) underwent PC-MRI measurements of flow in the left anterior descending coronary artery or one of its diagonal branches at rest and after administration of adenosine (140 microgram . kg(-1) . min (-1) IV). Immediately thereafter, intracoronary Doppler velocity (IDV) and flow measurements were made during cardiac catheterization at rest and after intravenous administration of adenosine. For the 12 patients, the correlation between MRI and invasive measurements of coronary arterial flow and coronary arterial flow reserve was excellent: coronary flow (MRI) (mL/min)= 0.85 x coronary flow (IDV) (mL/min)+17 (mL/min), r=.89, and coronary flow reserve (MRI) =0.79 x coronary velocity reserve (IDV) + 0.34, r=.89. For the range of coronary arterial flows (18 to 161 mL/min) measured by MRI, the limit of agreement between MRI and catheterization measurements of flow was -13+/-30 mL/min; for the range of coronary reserves (0.7 to 3.7) measured by MRI, the limit of agreement between the two techniques was 0.1+/-0.4., Conclusions: Cine velocity-encoded PC-MRI can noninvasively measure absolute coronary arterial flow in the left anterior descending artery in humans. PC-MRI can detect pharmacologically induced changes in coronary arterial flow and can reliably distinguish between those subjects with normal and abnormal coronary artery flow reserve.