Ferro-piezoelectricity in emerging Janus monolayer BMX2 (M = Ga, In and X = S, Se): ab initio investigations.

Nanoscale materials with inter-correlation characteristics are fundamental for developing high performance devices and applications. Hence theoretical research into unprecedented two-dimensional (2D) materials is crucial for improving understanding, especially when piezoelectricity is merged with other unique properties such as ferroelectricity. In this work, an unexplored 2D Janus family BMX2 (M = Ga, In and X = S, Se) corresponding to group-III ternary chalcogenides has been explored. The structural and mechanical stability, and optical and ferro-piezoelectric properties of BMX2 monolayers were investigated using first-principles calculations. We found that the lack of imaginary phonon frequencies in the phonon dispersion curves establishes the dynamic stability of the compounds. The monolayers BGaS2 and BGaSe2 are indirect semiconductors with bandgaps of 2.13 eV and 1.63 eV, respectively, while BInS2 is a direct semiconductor with a bandgap of 1.21 eV. BInSe2 is a novel zero-gap ferroelectric material with quadratic energy dispersion. All monolayers exhibit a high spontaneous polarization. The optical characteristics of the BInSe2 monolayer show high light absorption ranging from the infrared to the ultraviolet. The BMX2 structures exhibit in-plane and out-of-plane piezoelectric coefficients of up to 4.35 pm V-1 and 0.32 pm V-1. According to our findings, 2D Janus monolayer materials are a promising choice for piezoelectric devices.

Prospecting Lighting Applications with Ligand Field Tools and Density Functional Theory: A First-Principles Account of the 4f(7)-4f(6)5d(1) Luminescence of CsMgBr3:Eu(2+).

The most efficient way to provide domestic lighting nowadays is by light-emitting diodes (LEDs) technology combined with phosphors shifting the blue and UV emission toward a desirable sunlight spectrum. A route in the quest for warm-white light goes toward the discovery and tuning of the lanthanide-based phosphors, a difficult task, in experimental and technical respects. A proper theoretical approach, which is also complicated at the conceptual level and in computing efforts, is however a profitable complement, offering valuable structure-property rationale as a guideline in the search of the best materials. The Eu(2+)-based systems are the prototypes for ideal phosphors, exhibiting a wide range of visible light emission. Using the ligand field concepts in conjunction with density functional theory (DFT), conducted in nonroutine manner, we develop a nonempirical procedure to investigate the 4f(7)-4f(6)5d(1) luminescence of Eu(2+) in the environment of arbitrary ligands, applied here on the CsMgBr3:Eu(2+)-doped material. Providing a salient methodology for the extraction of the relevant ligand field and related parameters from DFT calculations and encompassing the bottleneck of handling large matrices in a model Hamiltonian based on the whole set of 33,462 states, we obtained an excellent match with the experimental spectrum, from first-principles, without any fit or adjustment. This proves that the ligand field density functional theory methodology can be used in the assessment of new materials and rational property design.

Development and applications of the LFDFT: the non-empirical account of ligand field and the simulation of the f-d transitions by density functional theory.

Ligand field density functional theory (LFDFT) is a methodology consisting of non-standard handling of DFT calculations and post-computation analysis, emulating the ligand field parameters in a non-empirical way. Recently, the procedure was extended for two-open-shell systems, with relevance for inter-shell transitions in lanthanides, of utmost importance in understanding the optical and magnetic properties of rare-earth materials. Here, we expand the model to the calculation of intensities of f → d transitions, enabling the simulation of spectral profiles. We focus on Eu(2+)-based systems: this lanthanide ion undergoes many dipole-allowed transitions from the initial 4f(7)((8)S7/2) state to the final 4f(6)5d(1) ones, considering the free ion and doped materials. The relativistic calculations showed a good agreement with experimental data for a gaseous Eu(2+) ion, producing reliable Slater-Condon and spin-orbit coupling parameters. The Eu(2+) ion-doped fluorite-type lattices, CaF2:Eu(2+) and SrCl2:Eu(2+), in sites with octahedral symmetry, are studied in detail. The related Slater-Condon and spin-orbit coupling parameters from the doped materials are compared to those for the free ion, revealing small changes for the 4f shell side and relatively important shifts for those associated with the 5d shell. The ligand field scheme, in Wybourne parameterization, shows a good agreement with the phenomenological interpretation of the experiment. The non-empirical computed parameters are used to calculate the energy and intensity of the 4f(7)-4f(6)5d(1) transitions, rendering a realistic convoluted spectrum.

Unusual cause of syncope in a 17 year-old young woman: left ventricular hydatid cyst.

Cardiac involvement in echinococcosis remains a singular finding, possibly associated with confusing symptomatology. We report the original case of a 17 year-old young woman, referred to our cardiology department for repeated exertion syncopes, and ultimately, proven through echocardiography, serologies and magnetic resonance imaging to have a massive hydatid cyst developing inside the left ventricular cavity towards the outflow tract. The cyst has been surgically completely removed with excellent results.

Total absence of ST-segment resolution after failed thrombolysis is correlated with unfavorable short- and long-term outcomes despite successful rescue angioplasty.

INTRODUCTION: ST-segment resolution (STR) is a well-established and simple tool for assessing the efficacy of reperfusion therapy in myocardial infarction. An incomplete (<50%) STR is a recognized marker of failed thrombolysis and a suitable recruitment criterion for rescue angioplasty. OBJECTIVE: We sought to determine the predictive value of the total absence of STR after thrombolysis in rescue angioplasty (percutaneous coronary intervention [PCI]). METHODS: Eighty-one consecutive patients who underwent a rescue angioplasty for failed thrombolysis in our institution from 2001 to 2007 were included. Two groups of patients were defined according to their STR extent, 90 minutes after lysis: partial resolution group 1 (10%-50% STR) vs absence of resolution group 2 (<10% STR) and compared in terms of in-hospital and long-term outcomes. RESULTS: Patients of group 2 were more likely to experience hemodynamic deterioration (50% vs 24%; odds ratio [OR] = 3.17; P = .017), to have a Thrombolysis in Myocardial Infarction 0 flow on the culprit artery (62.3% vs 42%; OR = 2.24; P = .045), to have a multivessel disease (66.7% vs 40%; OR = 3; P = .018), and to die during index hospitalization (26.7% vs 6%; OR = 5.69; P = .013) despite statistically similar rates of PCI failure in both groups (10% vs 7%; P = .402) and similar post-PCI STR (72% +/- 18.25% vs 75% +/- 11.62%; P = .36). In multivariate analysis, total absence of STR proved to be an independent predictor of in-hospital mortality (HR = 7.02; P = .032; 95% confidence interval, 1.18-41.58). Long-term major adverse cardiac events occurred more frequently in group 2 (log rank, P = .004) and were (on the Cox regression model) independently predicted by total absence of STR (HR = 6.21; P = .023; 95% confidence interval, 1.28-29.1). CONCLUSIONS: The STR assessment before rescue PCI proved to be a good and simple means to predict the short- and long-term prognosis in these patients.