Polytypism in GaAs nanowires: determination of the interplanar spacing of wurtzite GaAs by X-ray diffraction.

In GaAs nanowires grown along the cubic [111]c direction, zinc blende and wurtzite arrangements have been observed in their stacking sequence, since the energetic barriers for nucleation are typically of similar order of magnitude. It is known that the interplanar spacing of the (111)c Ga (or As) planes in the zinc blende polytype varies slightly from the wurtzite polytype. However, different values have been reported in the literature. Here, the ratio of the interplanar spacing of these polytypes is extracted based on X-ray diffraction measurements for thin GaAs nanowires with a mean diameter of 18-25 nm. The measurements are performed with a nano-focused beam which facilitates the separation of the scattering of nanowires and of parasitic growth. The interplanar spacing of the (111)c Ga (or As) planes in the wurtzite arrangement in GaAs nanowires is observed to be 0.66% ± 0.02% larger than in the zinc blende arrangement.

Influence of static atomic displacements on composition quantification of AlGaN/GaN heterostructures from HAADF-STEM images.

In an earlier publication Rosenauer et al. introduced a method for determination of composition in AlGaN/GaN heterostructures from high-angle annular dark field (HAADF) images. Static atomic displacements (SADs) were neglected during simulation of reference data because of the similar covalent radii of Al and Ga. However, SADs have been shown (Grillo et al.) to influence the intensity in HAADF images and therefore could be the reason for an observed slight discrepancy between measured and nominal concentrations. In the present study parameters of the Stillinger-Weber potential were varied in order to fit computed elastic constants, lattice parameters and bonding energies to experimental ones. A reference data set of HAADF images was simulated, in which the new parameterization was used to account for SADs. Two reference samples containing AlGaN layers with different Al concentrations were investigated and Al concentrations in the layers determined based on the new data set. We found that these concentrations were in good agreement with nominal concentrations as well as concentrations determined using alternative techniques such as strain state analysis and energy dispersive X-ray spectroscopy.

Improved survival of patients with coronary artery disease and low ejection fraction with ICD implantation versus conventional therapy in a real world survey.

BACKGROUND: Coronary artery disease (CAD) is associated with an increased risk for sudden cardiac death. Randomized controlled trials have shown that implantable cardioverter defibrillators (ICD) improve life expectancy unless they are implanted within the first days after an acute myocardial infarction and guidelines recommend their use. We aimed to validate that these results also apply to patients of a typical community hospital in Germany. METHODS: This was a retrospective analysis of patients undergoing coronary angiography in the Lippe-Detmold Hospital between 2003 and 2006. They had to have significant CAD and an ejection fraction (EF) ≤ 35% and no acute myocardial infarction within 28 days of implantation and no history of ventricular fibrillation. RESULTS: 213 patients were included; 70 of which received an ICD. Patients with an ICD implantation were younger (64.8 ± 9.9 vs. 67.9 ± 9.8 years; p = 0.034), had single vessel CAD more frequently (22.9 vs. 11.2%; p = 0.025) and a lower EF (26.7 ± 6.3 vs. 29.1 ± 4.6%; p = 0.006). Hospital readmissions were comparable between the ICD and the control group (68.6 vs. 72.0%; p = 0.602). ICD therapy was associated with a considerable survival benefit compared to conventional therapy (HR 0.52; 95%CI 0.29-0.93; p = 0.027) in a Cox-Proportional Hazards Regression analysis. CONCLUSIONS: Appreciating the potential limitations of retrospective studies, we found that ICD use was associated with improved survival in patients with significant CAD and an EF <= 35% typical for a large tertiary hospital.

Novel point mutations in the mitochondrial DNA detected in patients with dilated cardiomyopathy by screening the whole mitochondrial genome.

Dilated cardiomyopathy (DCM) is widely accepted as a pluricausal or multifactorial disease. Because of the linkage between energy metabolism in the mitochondria and cardiac muscle contraction, it is reasonable to assume that mitochondrial abnormalities may be responsible for some forms of DCM. We analysed the whole mitochondrial genome in a series of 45 patients with DCM for alterations and compared the findings with those of 62 control subjects. A total of 458 sequence changes could be identified. These sequence changes were distributed among the whole mitochondrial DNA (mtDNA). An increased number of novel missense mutations could be detected nearly in all genes encoding for protein subunits in DCM patients. In genes coding for NADH dehydrogenase subunits the number of mtDNA mutations detected in patients with DCM was significantly increased (p < 0.05) compared with control subjects. Eight mutations were found to occur in conserved amino acids in the above species. The c.5973G > A (Ala-Trp) and the c.7042T > G (Val-Asp) mutations were located in highly conserved domains of the gene coding for cytochrome c oxidase subunit. Two tRNA mutations could be detected in the mtDNA of DCM patients alone. The T-C transition at nt 15,924 is connected with respiratory enzyme deficiency, mitochondrial myopathy, and cardiomyopathy. The c.16189T > C mutation in the D-loop region that is associated with susceptibility to DCM could be detected in 15.6% of patients as well as in 9.7% of controls. Thus, mutations altering the function of the enzyme subunits of the respiratory chain can be relevant for the pathogenesis of dilated cardiomyopathy.