Comparative study of polar and semipolar (1122) InGaN layers grown by metalorganic vapour phase epitaxy

InGaN layers were grown simultaneously on (11¯22) GaN and (0001) GaN templates by metalorganic vapour phase epitaxy. At higher growth temperature ( 750oC), the indium content (<15%) of the (11¯22) and (0001) InGaN layers was similar. However, for temperatures less than 750oC, the indium content of the (11¯22) InGaN layers (15 - 26%) was generally lower than those with (0001) orientation (15 - 32%). The compositional deviation was attributed to the different strain relaxations between the (11¯22) and (0001) InGaN layers. Room temperature photoluminescence measurements of the (11¯22) InGaN layers showed an emission wavelength that shifts gradually from 380 nm to 580 nm with decreasing growth temperature (or increasing indium composition). The peak emission wavelength of the (11 ¯22) InGaN layers with an indium content of more than 10% blue-shifted a constant value of (50 - 60) nm when using higher excitation power densities. This blue-shift was attributed to band lling effects in the layers.This work was nancially supported by the EU-FP7 ALIGHT project, under agreement no. FP7-280587. This work was also partially supported by the Programme for Research in Third Level Institutions (PRTLI) fourth and fth cycles. SNA acknowledges nancial support for his postgraduate fellowship from the Iranian Ministry of Science, Research and Technology. PJP acknowledges nancial support for his Professorship from Science Foundation Ireland.This is the accepted manuscript. The final version is available from AIP at http://scitation.aip.org/content/aip/journal/jap/116/15/10.1063/1.489856

Myocardial Deformation in the Pediatric Age Group: Normal Values for Strain and Strain Rate Using 2D Magnetic Resonance Feature Tracking

Purpose To provide pediatric MR reference values for strain and strain rate for all four heart chambers. Study type Retrospective. Subjects One hundred and fifty-seven healthy children from two institutions (102 male, age 4.7-18 years). Field strength/sequence 1.5 T; balanced steady-state free precession sequence. Assessment Left ventricular (LV) global and regional longitudinal, circumferential, and radial strain and strain rate as well as right ventricular (RV) and atrial global and regional longitudinal strain and strain rate were measured in two-, three-, and four-chamber views and the short axis stack. The relationships between strain parameters and age, height, weight, and gender were investigated. Age- and height-specific centile curves and tables were created for LV strain and strain rate. For all other global strain parameters, the mean was calculated as a reference. Statistical tests Lambda-mu-sigma (LMS)-method of Cole and Green, univariable, and multivariable linear regression models. A P value <0.05 was considered to be statistically significant. Results Age, height and weight had a significant influence on LV global strain values. These parameters also showed an influence on RV strain but only in boys (girls P = 0.12) and none of the variables had a significant influence on atrial strain (P = 0.19-0.49). Gender differences were only found for RV strain values. Data conclusion Pediatric potential reference values for myocardial deformation parameters of both ventricles and atria are provided. The values may serve as a reference in future studies and clinical practice. Level of evidence 3 TECHNICAL EFFICACY: Stage 5

Pediatric Cardiac Magnetic Resonance Reference Values for Biventricular Volumes Derived From Different Contouring Techniques

Background Measurement of ventricular volumes and function using MRI is an important tool in pediatric congenital heart disease. However, normal values for children are sparce and analysis methods are inconsistent. Purpose To propose biventricular reference values in children for two MRI postprocessing (contouring) techniques. Study type Retrospective. Statistical tests Univariable and multivariable linear regression models were used to evaluate relationships between sex, weight, height, body surface area (BSA) and age and volumetric results. Reference graphs and tables were created with the LMS-method. Contouring techniques were compared by intraclass correlation, regression analysis and Bland-Altman plots. A P value < 0.05 was considered statistically significant. Results Height and BSA were significantly associated with LVESV (method 1) and with LVEDV and RVEDV (method 2). LVESV (method 2), RVESV (both methods), RVEDV (method 1), and LVEDMM and RVEDMM (both methods), showed significant associations with height and weight. LVSV and RVSV (both methods) were significantly associated with BSA and weight. RVESV (method 1) was significantly associated with age. Gender showed significant associations for all parameters. Data conclusion The proposed pediatric reference values can be used in the diagnosis and follow-up of congenital or acquired heart disease and for research purposes. Evidence level 3 TECHNICAL EFFICACY: Stage 2

The Complexity of Flat Freeze LTL

We consider the model-checking problem for freeze LTL on one-counter automata (OCAs). Freeze LTL extends LTL with the freeze quantifier, which allows one to store different counter values of a run in registers so that they can be compared with one another. As the model-checking problem is undecidable in general, we focus on the flat fragment of freeze LTL, in which the usage of the freeze quantifier is restricted. Recently, Lechner et al. showed that model checking for flat freeze LTL on OCAs with binary encoding of counter updates is decidable and in 2NEXPTIME. In this paper, we prove that the problem is, in fact, NEXPTIME-complete no matter whether counter updates are encoded in unary or binary. Like Lechner et al., we rely on a reduction to the reachability problem in OCAs with parameterized tests (OCAPs). The new aspect is that we simulate OCAPs by alternating two-way automata over words. This implies an exponential upper bound on the parameter values that we exploit towards an NP algorithm for reachability in OCAPs with unary updates. We obtain our main result as a corollary

Reference Values for Pediatric Atrial Volumes Assessed by Steady-State Free-Precession Magnetic Resonance Imaging Using Monoplane and Biplane Area-Length Methods

Field strength/sequence A 1.5 T; balanced steady-state free precession (bSSFP) sequence. Assessment The monoplane and biplane area-length methods were used to measure minimal and maximal left and right atrial volumes (LAmin , LAmax , RAmin , and RAmax ) from four-chamber (4ch) and two-chamber (2ch) MR cine images. Centile charts and tables for atrial volumes were created. Statistical tests Descriptive statistics, lambda-mu-sigma (LMS)-method of Cole and Green, univariable and multivariable linear regression models. A P value < 0.05 was considered to be statistically significant. Results In the multivariable linear model, body surface area was significantly associated with all atrial volumes and sex was significantly associated with RA volumes, LA volumes measured in the 2ch-view as well as biplane LAmax. Average atrial volumes measured: monoplane 4ch: LAmin 13.1 ± 4.8 mL/m2 , LAmax 33.4 ± 8.8 mL/m2 , RAmin 18.5 ± 6.8 mL/m2 , RAmax 33.2 ± 9.6 mL/m2 ; monoplane 2ch: LAmin 12.7 ± 4.9 mL/m2 , LAmax 30.5 ± 9.5 mL/m2 ; biplane: LAmin 12.3 ± 4.5 mL/m2 , LAmax 30.9 ± 8.7 mL/m2 . Data conclusion Pediatric MRI reference values for atrial volumes have been provided. Technical efficacy 2 EVIDENCE LEVEL: 4

Including diverse and admixed populations in genetic epidemiology research

The inclusion of ancestrally diverse participants in genetic studies can lead to new discoveries and is important to ensure equitable health care benefit from research advances. Here, members of the Ethical, Legal, Social, Implications (ELSI) committee of the International Genetic Epidemiology Society (IGES) offer perspectives on methods and analysis tools for the conduct of inclusive genetic epidemiology research, with a focus on admixed and ancestrally diverse populations in support of reproducible research practices. We emphasize the importance of distinguishing socially defined population categorizations from genetic ancestry in the design, analysis, reporting, and interpretation of genetic epidemiology research findings. Finally, we discuss the current state of genomic resources used in genetic association studies, functional interpretation, and clinical and public health translation of genomic findings with respect to diverse populations

Inelastic x-ray scattering at the National Synchrotron Light

The research program at the inelastic x-ray scattering beamline at the National Synchrotron Light Source is focused on the study of elementary excitations in condensed matter with total energy resolution on the order of 0.1 eV to 1.0 eV. Results from selected experiments are reported to demonstrate the capability of the beamline as well as the information can be obtained from inelastic x- ray scattering experiments

High bandwidth freestanding semipolar (11–22) InGaN/GaN light-emitting diodes

Freestanding semipolar (11–22) indium gallium nitride (InGaN) multiplequantum-well light-emitting diodes (LEDs) emitting at 445 nm have been realized by the use of laser lift-off (LLO) of the LEDs from a 50- m-thick GaN layer grown on a patterned (10–12) r -plane sapphire substrate (PSS). The GaN grooves originating from the growth on PSS were removed by chemical mechanical polishing. The 300 m × 300 m LEDs showed a turn-on voltage of 3.6 V and an output power through the smooth substrate of 0.87 mW at 20 mA. The electroluminescence spectrum of LEDs before and after LLO showed a stronger emission intensity along the [11–23]InGaN/GaN direction. The polarization anisotropy is independent of the GaN grooves, with a measured value of 0.14. The bandwidth of the LEDs is in excess of 150 MHz at 20 mA, and back-to-back transmission of 300 Mbps is demonstrated, making these devices suitable for visible light communication (VLC) applications