Bandgap Shrinkage and Charge Transfer in 2D Layered SnS2 Doped with V for Photocatalytic Efficiency Improvement.

Effects of electronic and atomic structures of V-doped 2D layered SnS2 are studied using X-ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X-ray absorption fine structure measurements at V K-edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS2 layers. X-ray absorption near-edge structure (XANES) reveals not only valence state of V dopant in SnS2 is ≈4+ but also the charge transfer (CT) from V to ligands, supported by V Lα,ß resonant inelastic X-ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo-excited electrons and effective carrier separation in layered SnS2 . Additionally, valence-band photoemission spectra and S K-edge XANES indicate that the density of states near/at valence-band maximum is shifted to lower binding energy in V-doped SnS2 compare to pristine SnS2 and exhibits band gap shrinkage. These findings support first-principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V-doped SnS2 .

A case of bronchopericardial fistula with tension pneumopericardium closed successfully by transpericardial intervention: A novel procedure.

A pneumopericardium is a collection of air or gas in the pericardial sac which may cause cardiac tamponade, known as tension pneumopericardium. Tension pneumopericardium is a rare and lethal presentation of bronchopericardial fistula. There are very few reports in the literature of patients surviving with this condition, although prompt diagnosis and early intervention are important. Treatment options are limited. We present a rare case of tension pneumopericardium with cardiogenic shock due to bronchopericardial fistula in a patient with bronchogenic carcinoma who was successfully treated with transpericardial intervention.

Catheter ablation of recurrent polymorphic tachycardia: Use of sodium channel blockade to organize the tachycardia: A case report.

A 55 year old male presented with recurrent implantable cardioverter defibrillator (ICD) shocks due to polymorphic ventricular tachycardia (PMVT). He had undergone prior catheter ablation for VT three years ago. During the prior attempt he underwent voltage guided substrate ablation. With programmed ventricular extrastimulation (PVES), PMVT was repeatedly induced requiring DC shock. Intravenous procainamide was administered and PVES was repeated which induced sustained monomorphic ventricular tachycardia (MMVT). This VT had pseudo delta waves with maximum deflection index of 0.68, suggestive of epicardial origin. Activation mapping was performed epicardially. Presystolic potentials were recorded in mid anterolateral wall of left ventricular epicardial region. Radiofrequency (RF) ablation at this site terminated the VT. Post ablation there was no inducible tachycardia and patient is free of arrhythmias during 2 years of follow-up.

Role of Interfacial Defects in Photoelectrochemical Properties of BiVO4 Coated on ZnO Nanodendrites: X-ray Spectroscopic and Microscopic Investigation.

Synchrotron-based X-ray spectroscopic and microscopic techniques are used to identify the origin of enhancement of the photoelectrochemical (PEC) properties of BiVO4 (BVO) that is coated on ZnO nanodendrites (hereafter referred to as BVO/ZnO). The atomic and electronic structures of core-shell BVO/ZnO nanodendrites have been well-characterized, and the heterojunction has been determined to favor the migration of charge carriers under the PEC condition. The variation of charge density between ZnO and BVO in core-shell BVO/ZnO nanodendrites with many unpaired O 2p-derived states at the interface forms interfacial oxygen defects and yields a band gap of approximately 2.6 eV in BVO/ZnO nanocomposites. Atomic structural distortions at the interface of BVO/ZnO nanodendrites, which support the fact that there are many interfacial oxygen defects, affect the O 2p-V 3d hybridization and reduce the crystal field energy 10Dq ∼2.1 eV. Such an interfacial atomic/electronic structure and band gap modulation increase the efficiency of absorption of solar light and electron-hole separation. This study provides evidence that the interfacial oxygen defects act as a trapping center and are critical for the charge transfer, retarding electron-hole recombination, and high absorption of visible light, which can result in favorable PEC properties of a nanostructured core-shell BVO/ZnO heterojunction. Insights into the local atomic and electronic structures of the BVO/ZnO heterojunction support the fabrication of semiconductor heterojunctions with optimal compositions and an optimal interface, which are sought to maximize solar light utilization and the transportation of charge carriers for PEC water splitting and related applications.

Correlation among photoluminescence and the electronic and atomic structures of Sr2SiO4:xEu3+ phosphors: X-ray absorption and emission studies.

A series of Eu3+-activated strontium silicate phosphors, Sr2SiO4:xEu3+ (SSO:xEu3+, x = 1.0, 2.0 and 5.0%), were synthesized by a sol-gel method, and their crystalline structures, photoluminescence (PL) behaviors, electronic/atomic structures and bandgap properties were studied. The correlation among these characteristics was further established. X-ray powder diffraction analysis revealed the formation of mixed orthorhombic α'-SSO and monoclinic ß-SSO phases of the SSO:xEu3+ phosphors. When SSO:xEu3+ phosphors are excited under ultraviolet (UV) light (λ = 250 nm, ~ 4.96 eV), they emit yellow (~ 590 nm), orange (~ 613 nm) and red (~ 652 and 703 nm) PL bands. These PL emissions typically correspond to 4f-4f electronic transitions that involve the multiple excited 5D0 → 7FJ levels (J = 1, 2, 3 and 4) of Eu3+ activators in the host matrix. This mechanism of PL in the SSO:xEu3+ phosphors is strongly related to the local electronic/atomic structures of the Eu3+-O2- associations and the bandgap of the host lattice, as verified by Sr K-edge and Eu L3-edge X-ray absorption near-edge structure (XANES)/extended X-ray absorption fine structure, O K-edge XANES and Kα X-ray emission spectroscopy. In the synthesis of SSO:xEu3+ phosphors, interstitial Eu2O3-like structures are observed in the host matrix that act as donors, providing electrons that are nonradiatively transferred from the Eu 5d and/or O 2p-Eu 4f/5d states (mostly the O 2p-Eu 5d states) to the 5D0 levels, facilitating the recombination of electrons that have transitioned from the 5D0 level to the 7FJ level in the bandgap. This mechanism is primarily responsible for the enhancement of PL emissions in the SSO:xEu3+ phosphors. This PL-related behavior indicates that SSO:xEu3+ phosphors are good light-conversion phosphor candidates for use in near-UV chips and can be very effective in UV-based light-emitting diodes.

Electronic, Electrical, and Magnetic Behavioral Change of SiO2-NP-Decorated MWCNTs.

Silicon-oxide-nanoparticle (SiO2-NP) heteroatoms were decorated/deposited onto multiwall carbon nanotube (MWCNT) surface to tune the properties of MWCNTs for electronic and magnetic applications. To achieve this objective, SiO2-NPs and MWCNTs were prepared and suspended together into toluene and heated at <100 °C for the formation of MWCNTs/SiO2-NP nanocomposites. A change in the microstructure, electronic, electrical, and magnetic behaviors of MWCNT nanocomposites decorated/deposited with silicon content was investigated using different techniques, viz., scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy for structural, compositional, and electronic structure, while current-voltage was used for electrical properties and field-dependent magnetization and electron spin resonance techniques were used for magnetic properties. The results indicated that SiO2-NPs adhered onto MWCNTs, resulting in variation in the material conductivity with the Si-NP content. The coercivity of MWCNT nanocomposites adhered with 1.5 atom % Si-NPs (H C@40 K = 689 Oe) is higher than that of those adhered with 5.75 atom % Si-NPs (H C@40 K = 357 Oe). In general, the results provide information about the possibilities of tuning the electronic, electrical, and magnetic properties of MWCNTs by adherence of SiO2-NPs onto them. This tuning of material properties could be useful for different electronic and magnetic device applications.

Catheter ablation for electrical storm in Brugada syndrome: Results of substrate based ablation.

BACKGROUND: Brugada syndrome (BrS) is known to cause malignant ventricular arrhythmia (VA) and sudden cardiac death (SCD). Patients with implantable cardioverter defibrillator (ICD) may experience recurrent shocks from ICD. Recent reports indicate that radiofrequency ablation (RFA) in BrS is feasible, and effective. Catheter ablation of premature ventricular complexes (PVCs) triggering VA and substrate modification of right ventricular outflow tract (RVOT) has been described. METHODS AND RESULTS: Five patients (4 males, age-23 to 32 years) with BrS and electrical storm (ES) despite being on isoprenaline infusion and cilostazol (phosphodiestrase-3 inhibitor) underwent 3 dimensional electroanatomic mapping and RFA. Ventricular fibrillation was easily inducible in two patients. Voltage map of right ventricle was created in sinus rhythm in all patients. Substrate modification of RVOT was performed endocardially in one patient, both endocardial and epicardial in three and only epicardially in one patient. Brugada pattern gradually resolved over one week in all patients post procedure. These patients completed follow up of median 40 months (1.5-70). One patient had inappropriate shock due to atrial fibrillation, one had an episode of VF and appropriate shock 24 months after the RFA. The remaining four patients had no device therapy or VA in device log on follow up. CONCLUSION: Abnormal myocardial substrate is observed in RVOT among patients with BrS. Substrate modification in these patients may abolish Brugada pattern on the ECG and prevents spontaneous VAs on long term follow up.

Prognostic value of fluorine-18 fluoro-2-deoxyglucose positron emission computed tomography in patients with unexplained atrioventricular block.

BACKGROUND: The cause of atrioventricular conduction block (AVB) remains unexplained in a significant number of patients. Granulomatous myocarditis is an uncommon but important cause of AVB. Fluorine-18 fluoro-2-deoxyglucose positron emission computed tomography (18-FDG PET) scan has emerged as a sensitive tool for diagnosing granulomatous myocarditis. OBJECTIVE: The purpose of this study was to evaluate the prognostic value of 18-FDG PET scan in patients with unexplained AVB. METHODS: Patients age 18-55 years presenting with unexplained AVB and requiring a permanent pacemaker were evaluated with a fasting 18-FDG PET scan. Transthoracic echocardiography was performed at baseline and at follow-up. Major adverse cardiac events (ventricular tachycardia, heart failure, cardiac death) were noted during follow-up. RESULTS: Over a period of 3 years, 35 patients (20 females, 15 males; mean age 43.67 ± 11.21 years) were included in the study. Abnormal myocardial FDG uptake was noted in 15 patients (42.8%). Four patients consented for biopsy of paracardiac FDG avid lymph nodes, which revealed granulomatous inflammation (one of which grew Mycobacterium tuberculosis in culture). Mean follow-up period was 24 months. Major adverse cardiac events were significantly higher in the patients with abnormal PET uptake (P < .01) compared to those with normal scans. CONCLUSION: Patients with high-degree AVB and abnormal myocardial 18-FDG PET uptake have more adverse cardiac events and worse outcomes. Early screening for myocardial inflammation and appropriate treatment may prevent these complications. Tuberculosis may be an important cause of unexplained AVB, apart from sarcoidosis, in developing countries such as India.

Serial FDG-PET scans help to identify steroid resistance in cardiac sarcoidosis.

BACKGROUND: Cardiac sarcoidosis (CS) is increasingly being recognized. Immunosuppression with corticosteroids is the mainstay of therapy. But the optimal dose of steroids and how to assess response to therapy is not known. Prognosis is poor if these patients are untreated or undertreated. Fluorine-18-flurodeoxyglucose positron emission computed tomography (18FDG-PET CT) is a sensitive tool in diagnosing CS. It correlates closely with the level of granulomatous inflammation and can be used to monitor response to therapy. METHODS: We identified 15 patients (6 women; mean age, 42.9±12.5years) based on histopathological diagnosis. All had a baseline and follow-up fasting 18FDG-PET CT scans before and after steroid therapy. Non-responders were defined as those in whom ventricular arrhythmias, symptoms of HF and left ventricular systolic function and/or ventricular arrhythmias did not improve or worsened despite steroid therapy. FDG uptake of involved myocardium and lymph nodes (LN) was compared in clinical responders and non-responders on follow-up. RESULTS: Of the 15 patients, 4 were clinical non-responders to steroid therapy. Follow-up 18FDG-PET CT was performed at 125.8±54.2days after the initiation of steroid therapy. Myocardial maximum standardized uptake of FDG (SUVmax) value decreased significantly in responders (p=0.004) while there was an increase in non-responders (p<0.05) on follow-up. Number of left ventricle (LV) segments with FDG uptake significantly decreased in responders (p=0.007), and on increasing trend in non-responders (p=0.465). Heterogeneous FDG uptake on baseline PET scan, increase in intensity as well as area of myocardial inflammation on follow-up PET scan was associated with poor clinical outcome despite steroid therapy. CONCLUSIONS: Serial 18FDG-PET CT scans can be used to monitor steroid therapy in active CS. Increase in PET uptake after steroid therapy correlates with poor clinical outcome. Repeat PET scan may help to predict steroid-resistant CS and the need for up-titration of immunosuppressive therapy among poor responders to initial therapy.

A novel approach in the use of radiofrequency catheter ablation of septal hypertrophy in hypertrophic obstructive cardiomyopathy.

OBJECTIVE: Alcohol septal ablation (ASA) is a therapeutic alternative to surgical myectomy in patients with hypertrophic obstructive cardiomyopathy (HOCM). However, the anatomical variability of the septal branch, risk of complete heart block, and late onset ventricular arrhythmias are limitations to its therapeutic usage. There is recent interest in the use of radiofrequency catheter ablation (RFCA) as a therapeutic option in HOCM. We aimed to assess the safety and efficacy of RFCA in the treatment of symptomatic HOCM. METHODS: Seven patients with symptomatic HOCM (mean age 43.7±15.6 years, five males), and significant left ventricular outflow tract (LVOT) gradient despite optimal drug therapy, underwent ablation of the hypertrophied interventricular septum. These patients had unfavorable anatomy for ASA. Ablation was performed under 3D electro-anatomical system guidance using an open irrigated tip catheter. The region of maximal LV septal bulge as seen on intracardiac echocardiography was targeted. Patients were followed up at 1, 6, and 12 months post-procedure. RESULTS: The mean baseline LVOT gradient by Doppler echocardiography was 81±14.8mm of Hg which reduced to 48.5±22.6 (p=0.0004), 49.8±19.3 (p=0.0004), and 42.8±26.1mm of Hg (p=0.05) at 1, 6, and 12 months respectively. Symptoms improved at least by one NYHA class in all but one patient. One patient developed transient pulmonary edema post-RFA. There were no other complications. CONCLUSION: RFCA of the hypertrophied septum causes sustained reduction in the LVOT gradient and symptomatic improvement among patients with HOCM. Electroanatomical mapping helps to perform the procedure safely.

Contact angle measurements: a preliminary diagnostic tool for evaluating the performance of ZnFe2O4 nano-flake based supercapacitors.

Contact angle measurements (surface wettability) of the electrolytes (1 M KOH, NaOH and LiOH) and their combination (1 M 1 : 1 v/v LiOH + KOH, NaOH + KOH and LiOH + NaOH) in contact with ZnFe2O4 nano-flake based electrodes is used as an empirical diagnostic tool to pre-evaluate the performance of a supercapacitor prior to actual fabrication of the device.

A stepwise approach to the induction of idiopathic fascicular ventricular tachycardia.

PURPOSE: Noninducibility of the clinical tachycardia is a major limitation while mapping and ablating idiopathic fascicular ventricular tachycardia (FVT). There is very little data on systematic induction protocols in this entity. Our aim was to study the role of systematic induction protocols in patients with clinically documented ventricular tachycardia (VT). METHODS: Programmed electrical stimulation was performed at baseline from high right atrium, right ventricular apex, right ventricular outflow tract and from left ventricle as per the protocol. Programmed ventricular stimulation was performed at two drive cycle lengths up to three extrastimuli and short-long-short sequence. If FVT remained non inducible at baseline, pharmacological provocation with isoprenaline/atropine/phenylephrine was used based on the baseline atrio-ventricular Wenckebach cycle length. RESULTS: This systematic induction protocol was studied in 68 patients with clinically documented FVT and sustained FVT was inducible in 64 patients (94 %). Of these 64 patients, pharmacological provocation was required in 18 patients (28 %) while in the remaining, sustained VT was induced at baseline. This high induction rate allowed ablation during tachycardia, which resulted in 100 % acute procedural success in the patients where sustained tachycardia could be induced. At a follow up of 29 ± 13 months, two patients (3 %) had recurrence. CONCLUSIONS: Systematic induction protocol along with the appropriate use of pharmacological agents results in a high induction rate of FVT. This may result in more defined and limited ablation during tachycardia with better success rates and lesser recurrence.

Unexpected difficulty during transcatheter device closure of atrial septal defect associated with right aortic arch.

Right aortic arch (RAA) associated with isolated atrial septal defect (ASD) is very rare. We report successful closure of ASD associated with RAA using a 26-mm atrial septal occluder in a 30-year-old male patient. The impingement of right descending aorta in RAA caused malposition of the device in the left atrium. Deployment of the device through the right upper pulmonary vein successfully closed the defect. Follow-up evaluation by computerized tomography scan and echocardiogram showed no pulmonary venous obstruction.