A Layered Tin Bismuth Selenide with Three Different Building Blocks that Account for an Extremely Large Lattice Parameter of 283 Å

The layered compound Sn2.8(4) Bi20.2(4) Se27 exhibits an extraordinarily long-periodic 150R stacking sequence. The crystal structure contains three different building blocks, which form upon the addition of Sn to a Bi-rich bismuth selenide. Sn-doped Bi2 double ("2") layers similar to those in elemental bismuth, Sn0.3 Bi1.7 Se3 quintuple ("5") layers and Sn0.4 Bi2.6 Se4 septuple ("7") layers are arranged in a 7525757525|7525757525|7525757525 sequence, which corresponds to a structure with a=4.1819(4) and c=282.64(6) Å in space group R 3 ‾ m. The structure of a microcrystal was determined using microfocused synchrotron radiation and refined as a formally commensurately modulated structure in (3+1)D superspace (superspace group R 3 ‾ m(00γ)00), with a trivial basic structure that contains just one atom. The stacking sequence as well as the cation distribution are confirmed by aberration-corrected scanning transmission electron microscopy (STEM) in combination with chemical mapping by X-ray spectroscopy with atomic resolution. Stacking faults are not typical but have been observed occasionally.

Structure and thermoelectric properties of the silver lead bismuth selenides Ag5Pb9Bi19Se40 and AgPb3Bi7Se14

In the system Ag/Pb/Bi/Se, two new thermoelectric phases derived from lillianite (Pb3Bi2S6) have been characterized. The crystal structures correspond to the 8,8L- and 5,5L-types, respectively, both in the space group Cmcm. The room-temperature unit-cell parameters of 8,8L-Ag5Pb9Bi19Se40 are a = 4.2151(8) Å, b = 13.951(3) Å and c = 35.284(7) Å and those of 5,5L-AgPb3Bi7Se14 are a = 4.2337(8) Å, b = 13.864(2) Å and c = 24.653(3) Å. The temperature-dependent evolution of the lattice parameters of Ag5Pb9Bi19Se40 becomes steeper at temperatures above 300 °C and hints at the mobility of Ag+ ions. Samples containing both phases exhibit thermoelectric figures of merit up to ZT = 0.23 at 250 °C. HRTEM investigations on such samples showed well-ordered areas of the lillianite-like phases separated by large slabs that exhibit a high concentration of defects and may compensate for lattice misfits between the lillianite-type phases.

Cornucopia of Structures in the Pseudobinary System (SnSe) xBi2Se3: A Crystal-Chemical Copycat

Pseudobinary phases (SnSe) _xBi₂Se₃ exhibit a very diverse structural chemistry characterized by different building blocks, all of which are cutouts of the NaCl type. For SnSe contents between x = 5 and x = 0.5, several new phases were discovered. Next to, for example, Sn₄Bi₂Se₇ ( x = 4) in the NaCl structure type and SnBi₄Se₇ ( x = 0.5) in the layered defect GeSb₂Te₄ structure type, there are at least four compounds (0.8 ≤ x ≤ 3) with lillianite-like structures built up from distorted NaCl-type slabs (L4,4-type Sn_2.22Bi_2.52Se₆, L4,5-type Sn_9.52Bi_10.96Se₂₆, L4,7-type Sn_11.49Bi_12.39Se₃₀, and L7,7-type Sn_3.6Bi_3.6Se₉). For two of them (L4,7 and L7,7), the cation distributions were determined by resonant X-ray scattering, which also confirmed the presence of significant amounts of cation vacancies. Thermoelectric figures of merit ZT range from 0.04 for Sn₄Bi₂Se₇ to 0.2 for layered SnBi₄Se₇; this is similar to that of the related compounds SnBi₂Te₄ or PbBi₂Te₄. Compounds of the lillianite series exhibit rather low thermal conductivities (∼0.75 W/mK for maximal ZT). More than other "sulfosalts", compounds in the pseudobinary system SnSe-Bi₂Se₃ adapt to changes in the cation-anion ratio by copying structure types of compounds containing lighter or heavier homologues of Sn, Bi, or Se and can incorporate significant amounts of vacancies. Thus, (SnSe) _xBi₂Se₃ is a multipurpose model system with vast possibilities for substitutional and structural modification aiming at the optimization of thermoelectric or other properties.

An unusual nitride network of aluminum-centered octahedra and phosphorus-centered tetrahedra and structure determination from microcrystalline samples

Aluminum coordinated by six nitrogen atoms was realized in a new highly condensed network which was obtained via HP–HT synthesis at 5 GPa.

[Idiopathic left ventricular tachycardia in childhood: typical clinical findings and different therapeutic options]

We report 3 adolescents with structurally normal heart who were referred to hospital due to long-lasting palpitations. Initial 12-lead-ECG showed sustained, monomorphic ventricular tachycardia, right bundle branch block QRS morphology and axis deviation. After failure of different anti-arrhythmic drugs finally the intravenous medication with verapamil led to termination of ventricular tachycardia in all three patients. All clinical findings and the responsiveness to verapamil are consistent with the diagnosis of idiopathic left ventricular tachycardia. In one patient an electrophysiological study was done and increased left ventricular vulnerability was shown. After inducing a tachycardia originating from the left ventricle radiofrequency catheter ablation of the left-posterior fascicle was successfully performed. The tachycardia was not inducible after this ablation. Since that investigation the patient has been asymptomatic without anti-arrhythmic treatment. Two of three patients have been on oral verapamil prophylactically and have been free of symptoms.

Capofungin therapy for Aspergillus lung infection in a boy with chronic granulomatous disease

Neutrophils of patients with chronic granulomatous disease (CGD) are profoundly defective in killing microorganisms. As in patients with chemotherapy-induced neutropenia, CGD patients are highly susceptible to life-threatening invasive Aspergillus infections, and conventional antimycotic treatment is not always successful. The new drug, caspofungin, was used to treat Aspergillus lung infection in one child with CGD.

A stepwise mapping approach for localization and ablation of ectopic right, left, and septal atrial foci using electroanatomic mapping

AIMS

We describe a new strategic stepwise mapping approach for fast and accurate identification and ablation of ectopic atrial foci using an electroanatomic mapping system.

METHODS AND RESULTS

Mapping procedures started with the acquisition of four points at the superior/septal part of the tricuspid annulus. According to this activation sequence, maps were continued towards the right atrial free wall if relatively early activation was shown at the superior part of the initial map or towards the triangle of Koch and, if necessary, to the left atrium, in cases of relatively early activation at the septum. High density mapping and detailed electrogram analysis only of the target area allowed identification and ablation of 34 foci in 30 of the 32 studied consecutive patients. A small number of mapping points were sufficient within a procedure time of 90 +/- 41 min for right 148 +/- 68 min and for left sided foci and a total fluoroscopy time of 9.6 +/- 7.2 min and 24.8 +/- 16.4 min respectively. Sixteen foci were located at the right free wall, eight at the left free wall, and 10 at the right or left side of the septum.

CONCLUSION

Strategic electroanatomic mapping with fast identification of the area of tachycardia origin and high density mapping only of this target area allowed fast and successful localization and ablation of right and left free wall and septal ectopic atrial foci.