Electric‐field dependence of acceptor‐level binding energies in strained SiGe and InGaAs quantum‐well structures

The acceptor energies for strained SiGe (on Si) and InGaAs (on GaAs) quantum wells are calculated from a 4×4 k⋅p band structure that includes the effects of strain and electric fields. Both center‐ and edge‐doped cases are examined. The theory shows marked changes in the acceptor energies with both strain and electric field. The wide variation in binding energy for the edge‐doped quantum wells may provide a mechanism for tunable far‐infrared detectors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70960/2/JAPIAU-71-4-2023-1.pd

Comparison of mode suppression and large signal modulation between lattice matched and strained InGaAs/AlGaAs quantum well lasers

Numerical techniques are developed to study the output spectra and to solve the coupled mode rate equations for InxGa1−xAs/Al0.3Ga0.7As quantum well lasers. The optical properties of the laser are calculated from a 4×4 k⋅p band structure which includes the effects of strain. We find that the side modes are severely suppressed in the strained laser. Large signal switching of the laser is also studied and the role of strain is identified in the device response. If the laser is switched from the off state to a state of given photon density in the lasing mode, then the strained system exhibits a faster time response. If, however, the laser is switched from the off state to a state of given total photon density, then the strained system has a slower time response.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70732/2/APPLAB-59-19-2381-1.pd

Calculations of the electric field dependent far‐infrared absorption spectra in InAs/AlGaSb quantum wells

Excitonic and band‐to‐band absorption spectra are calculated for vertical incident radiation for the InAs/AlGaSb multiple quantum well structures. Due to the special band lineup of this heterostructure, the absorption spectra can be tailored to respond in far infrared. The electric field dependence of the spectra shows blue shift and enhanced absorption in contrast to the situation in type I quantum wells. Applications to far infrared detectors are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70612/2/APPLAB-55-9-888-1.pd

Refractive index and electro‐optic effect in compressive and tensile strained quantum wells

The effects of biaxial compressive and tensile strain on the excitonic resonances and associated changes in refractive index and electro‐optic effect in quantum wells have been calculated and measured. Theoretical calculations include the important heavy‐hole–light–hole band mixing effects. It is seen that the excitonic contributions dominate near the band edge. With increasing compressive strain the linear electro‐optic effect is slightly increased, while the quadratic effect is greatly enhanced. The effects are reversed in quantum wells under tensile strain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70690/2/JAPIAU-69-7-4071-1.pd

Effect of coherent strain on hydrogenic acceptor levels in InyGa1−yAs/AlxGa1−xAs quantum well structures

The biaxial strain produced in lattice‐mismatched epitaxy can have a substantial effect on the valence band structure. Theoretical results are presented for a hydrogenic acceptor in a quantum well under tensile and compressive strain. The acceptor level energy is a strong function of strain and could be used as a signature for the effect of strain on the valence band structure. Experimental studies are carried out on compressively strained InyGa1−yAs/ AlxGa1−xAs quantum well structures and the acceptor level energy is determined by photoluminescence measurements. Good agreement is found with the experiments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70617/2/APPLAB-57-2-180-1.pd

Race and Vitamin D Binding Protein Gene Polymorphisms Modify the Association of 25-Hydroxyvitamin D and Incident Heart Failure: The ARIC (Atherosclerosis Risk in Communities) Study

Abstract Objectives This study sought to determine if low serum 25-hydroxyvitamin D (25[OH]D) is associated with incident heart failure (HF) and if the association is: 1) partly mediated by traditional cardiovascular risk factors; 2) stronger among whites than blacks; and 3) stronger among those genetically predisposed to having high levels of vitamin D binding protein (DBP).Background Suboptimal 25(OH)D is a potential cardiovascular risk factor.Methods A total of 12,215 ARIC (Atherosclerosis Risk in Communities) study participants free of HF at baseline (1990 to 1992; median age, 56; 24% black) were followed through 2010. Total serum 25(OH)D was measured at baseline using liquid chromatography–mass spectrometry. Incident HF events were identified by a hospital discharge code of ICD9-428 and parallel International Classification of Diseases codes for HF deaths.Results During 21 years of follow-up, 1,799 incident HF events accrued. The association between 25(OH)D and HF varied by race (p-interaction = 0.02). Among whites, risk was 2-fold higher for those in the lowest (≤17 ng/ml) versus highest (≥31 ng/ml) quintile of 25(OH)D. The association was attenuated but remained significant with covariate adjustment. In blacks there was no overall association. In both races, those with low 25(OH)D and the rs7041 G allele, which predisposes to high DBP, were at greater risk (p-interaction = 0.01).Conclusions Low serum 25(OH)D was independently associated with incident HF among whites, but not among blacks. However, in both races, low 25(OH)D was associated with HF risk among those genetically predisposed to high DBP. These findings provide novel insight into metabolic differences that may underlie racial variation in the association between 25(OH)D and cardiovascular risk

Genome-wide association studies identify CHRNA5/3 and HTR4 in the development of airflow obstruction

RATIONALE: Genome-wide association studies (GWAS) have identified loci influencing lung function, but fewer genes influencing chronic obstructive pulmonary disease (COPD) are known.OBJECTIVES: Perform meta-analyses of GWAS for airflow obstruction, a key pathophysiologic characteristic of COPD assessed by spirometry, in population-based cohorts examining all participants, ever smokers, never smokers, asthma-free participants, and more severe cases.METHODS: Fifteen cohorts were studied for discovery (3,368 affected; 29,507 unaffected), and a population-based family study and a meta-analysis of case-control studies were used for replication and regional follow-up (3,837 cases; 4,479 control subjects). Airflow obstruction was defined as FEV(1) and its ratio to FVC (FEV(1)/FVC) both less than their respective lower limits of normal as determined by published reference equations.MEASUREMENTS AND MAIN RESULTS: The discovery meta-analyses identified one region on chromosome 15q25.1 meeting genome-wide significance in ever smokers that includes AGPHD1, IREB2, and CHRNA5/CHRNA3 genes. The region was also modestly associated among never smokers. Gene expression studies confirmed the presence of CHRNA5/3 in lung, airway smooth muscle, and bronchial epithelial cells. A single-nucleotide polymorphism in HTR4, a gene previously related to FEV(1)/FVC, achieved genome-wide statistical significance in combined meta-analysis. Top single-nucleotide polymorphisms in ADAM19, RARB, PPAP2B, and ADAMTS19 were nominally replicated in the COPD meta-analysis.CONCLUSIONS: These results suggest an important role for the CHRNA5/3 region as a genetic risk factor for airflow obstruction that may be independent of smoking and implicate the HTR4 gene in the etiology of airflow obstruction.</p

Association of Forced Vital Capacity with the Developmental Gene <i>NCOR2</i>

Background Forced Vital Capacity (FVC) is an important predictor of all-cause mortality in the absence of chronic respiratory conditions. Epidemiological evidence highlights the role of early life factors on adult FVC, pointing to environmental exposures and genes affecting lung development as risk factors for low FVC later in life. Although highly heritable, a small number of genes have been found associated with FVC, and we aimed at identifying further genetic variants by focusing on lung development genes. Methods Per-allele effects of 24,728 SNPs in 403 genes involved in lung development were tested in 7,749 adults from three studies (NFBC1966, ECRHS, EGEA). The most significant SNP for the top 25 genes was followed-up in 46,103 adults (CHARGE and SpiroMeta consortia) and 5,062 chi

Genome-wide association analysis identifies six new loci associated with forced vital capacity

Forced vital capacity (FVC), a spirometric measure of pulmonary function, reflects lung volume and is used to diagnose and monitor lung diseases. We performed genome-wide association study meta-analysis of FVC in 52,253 individuals from 26 studies and followed up the top associations in 32,917 additional individuals of European ancestry. We found six new regions associated at genome-wide significance (P < 5 × 10−8) with FVC in or near EFEMP1, BMP6, MIR129-2–HSD17B12, PRDM11, WWOX and KCNJ2. Two loci previously associated with spirometric measures (GSTCD and PTCH1) were related to FVC. Newly implicated regions were followed up in samples from African-American, Korean, Chinese and Hispanic individuals. We detected transcripts for all six newly implicated genes in human lung tissue. The new loci may inform mechanisms involved in lung development and the pathogenesis of restrictive lung disease

Genome-wide association study identifies six new loci influencing pulse pressure and mean arterial pressure.

Numerous genetic loci have been associated with systolic blood pressure (SBP) and diastolic blood pressure (DBP) in Europeans. We now report genome-wide association studies of pulse pressure (PP) and mean arterial pressure (MAP). In discovery (N = 74,064) and follow-up studies (N = 48,607), we identified at genome-wide significance (P = 2.7 × 10(-8) to P = 2.3 × 10(-13)) four new PP loci (at 4q12 near CHIC2, 7q22.3 near PIK3CG, 8q24.12 in NOV and 11q24.3 near ADAMTS8), two new MAP loci (3p21.31 in MAP4 and 10q25.3 near ADRB1) and one locus associated with both of these traits (2q24.3 near FIGN) that has also recently been associated with SBP in east Asians. For three of the new PP loci, the estimated effect for SBP was opposite of that for DBP, in contrast to the majority of common SBP- and DBP-associated variants, which show concordant effects on both traits. These findings suggest new genetic pathways underlying blood pressure variation, some of which may differentially influence SBP and DBP