2 research outputs found
Effect of Growth Induced (Non)Stoichiometry on the Structure, Dielectric Response, and Thermal Conductivity of SrTiO<sub>3</sub> Thin Films
We report dramatic variations in cation stoichiometry
in SrTiO<sub>3</sub> thin films grown via pulsed laser deposition
and the implications
of this nonstoichiometry for structural, dielectric, and thermal properties.
The chemical composition of SrTiO<sub>3</sub> thin films was characterized
via X-ray photoelectron spectroscopy and Rutherford backscattering
spectrometry. These studies reveal that deviations in laser fluence
and deposition geometry can result in deviations of cation stoichiometry
as large as a few percent. Additionally, X-ray diffraction was used
to probe structural evolution and revealed an asymmetric strain relaxation
mechanism in which films possessing Sr-excess undergo relaxation before
those possessing Sr-deficiency. Furthermore, the dielectric constant
decreases and the loss tangent increases with increasing nonstoichiometry
with intriguing differences between Sr-excess and -deficiency. Thermal
conductivity is also found to be sensitive to nonstoichiometry, with
Sr-excess and -deficiency resulting in 65% and 35% reduction in thermal
conductivity, respectively. These trends are explained by the expected
defect structures
Loss-of-function mutations in APOC3, triglycerides, and coronary disease
BACKGROUND: Plasma triglyceride levels are heritable and are correlated with the risk of coronary heart disease. Sequencing of the protein-coding regions of the human genome (the exome) has the potential to identify rare mutations that have a large effect on phenotype. METHODS: We sequenced the protein-coding regions of 18,666 genes in each of 3734 participants of European or African ancestry in the Exome Sequencing Project. We conducted tests to determine whether rare mutations in coding sequence, individually or in aggregate within a gene, were associated with plasma triglyceride levels. For mutations associated with triglyceride levels, we subsequently evaluated their association with the risk of coronary heart disease in 110,970 persons. RESULTS: An aggregate of rare mutations in the gene encoding apolipoprotein C3 (APOC3) was associated with lower plasma triglyceride levels. Among the four mutations that drove this result, three were loss-of-function mutations: a nonsense mutation (R19X) and two splice-site mutations (IVS2+1G→A and IVS3+1G→T). The fourth was a missense mutation (A43T). Approximately 1 in 150 persons in the study was a heterozygous carrier of at least one of these four mutations. Triglyceride levels in the carriers were 39% lower than levels in noncarriers (P<1×10(-20)), and circulating levels of APOC3 in carriers were 46% lower than levels in noncarriers (P=8×10(-10)). The risk of coronary heart disease among 498 carriers of any rare APOC3 mutation was 40% lower than the risk among 110,472 noncarriers (odds ratio, 0.60; 95% confidence interval, 0.47 to 0.75; P=4×10(-6)). CONCLUSIONS: Rare mutations that disrupt APOC3 function were associated with lower levels of plasma triglycerides and APOC3. Carriers of these mutations were found to have a reduced risk of coronary heart disease. (Funded by the National Heart, Lung, and Blood Institute and others.)