| 1. |
- Yang, S, et al.
(författare)
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Improvement of Crystalline and Photoluminescence of Atomic Layer Deposited m-Plane ZnO Epitaxial Films by Annealing Treatment
- 2012
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Ingår i: Crystal Growth & Design. - : American Chemical Society. - 1528-7483 .- 1528-7505. ; 12:10, s. 4745-4751
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Tidskriftsartikel (refereegranskat)abstract
- Monocrystalline m-plane ZnO epitaxial films with flat surface morphology were grown on m-plane sapphire by using atomic layer deposition. X-ray diffraction and transmission electron microscopy measurements verify not only the in-plane epitaxial relationship of the as-grown films as (10 (1) over bar0)andlt; 0001 andgt;(ZnO)parallel to(10 (1) over bar0)andlt;(1) over bar2 (1) over bar0 andgt; Al2O3 but also the absence of domains with undesirable orientations, which are generally obtained in the m-plane ZnO films grown by other methods. Experimental results indicate that the basal plane stacking fault (BSF) is the dominant structural defects that contribute to the emission at 3.31 eV in m-plane ZnO films. Exactly how thermal annealing affects the structural and optical properties of ZnO epi-films was also investigated. Additionally, based on time-resolved photoluminescence at 5 K, the decay time of BSF related emission and near-band-edge (NBE) emission were determined. Results of this work further demonstrated that the decay time of NBE emission increases with a higher annealing temperature, accompanied by an improvement in crystal structure.
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| 2. |
- Yang, S., et al.
(författare)
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Recombination dynamics of a localized exciton bound at basal stacking faults within the m-(p)lane ZnO film
- 2014
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 105:1, s. 011106-
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the carrier dynamics near basal stacking faults (BSFs) in m-plane ZnO epitaxial film. The behaviors of the type-II quantum wells related to the BSFs are verified through time-resolved and time-integrated photoluminescence. The decay time of the emission of BSFs is observed to have a higher power law value and longer decay time than the emission of the donor-bound excitons. The spectral-dependent decay times reveal a phenomenon of carriers migrating among band tail states, which are related to the spatial distribution of the type-II quantum wells formed by the BSFs. A high density of excited carriers leads to a band bending effect, which in turn causes a blue-shift of the emission peak of BSFs with a broadened distribution of band tail states.
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| 3. |
- Bartels-Rausch, T., et al.
(författare)
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A review of air-ice chemical and physical interactions (AICI): Liquids, quasi-liquids, and solids in snow
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:3, s. 1587-1633
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Tidskriftsartikel (refereegranskat)abstract
- Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air-ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed. © Author(s) 2014.
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| 4. |
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| 5. |
- Curtis, Bruce A., et al.
(författare)
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Algal genomes reveal evolutionary mosaicism and the fate of nucleomorphs
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 492:7427, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- Cryptophyte and chlorarachniophyte algae are transitional forms in the widespread secondary endosymbiotic acquisition of photosynthesis by engulfment of eukaryotic algae. Unlike most secondary plastid-bearing algae, miniaturized versions of the endosymbiont nuclei (nucleomorphs) persist in cryptophytes and chlorarachniophytes. To determine why, and to address other fundamental questions about eukaryote-eukaryote endosymbiosis, we sequenced the nuclear genomes of the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans. Both genomes have >21,000 protein genes and are intron rich, and B. natans exhibits unprecedented alternative splicing for a single-celled organism. Phylogenomic analyses and subcellular targeting predictions reveal extensive genetic and biochemical mosaicism, with both host-and endosymbiont-derived genes servicing the mitochondrion, the host cell cytosol, the plastid and the remnant endosymbiont cytosol of both algae. Mitochondrion-to-nucleus gene transfer still occurs in both organisms but plastid-to-nucleus and nucleomorph-to-nucleus transfers do not, which explains why a small residue of essential genes remains locked in each nucleomorph.
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| 6. |
- Chatterjee, Sanjukta, et al.
(författare)
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Mechanical reinforcement and thermal conductivity in expanded graphene nanoplatelets reinforced epoxy composites
- 2012
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 531, s. 6-10
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Tidskriftsartikel (refereegranskat)abstract
- Influence of reinforcements on mechanical and thermal properties of graphene nanoplatelets/epoxy composites is investigated. Amine functionalized expanded graphene nanoplatelets (EGNPs) were dispersed within epoxy resins using high-pressure processor followed by three roll milling. Functionality on the EGNPs was confirmed with FTIR and micro-Raman spectroscopy. Bending and nano-mechanical testing was performed on the composites. Incorporation of EGNPs improved the flexural modulus and hardness of the composite and increased fracture toughness by up to 60%. Marked improvement was observed in thermal conductivity of the composites reaching 36% at 2 wt.% loading. Functionalized EGNPs exhibited significant improvements indicating favorable interaction at EGNPs/polymer interface.
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| 7. |
- Jaiswal, Siddhartha, et al.
(författare)
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Age-Related Clonal Hematopoiesis Associated with Adverse Outcomes.
- 2014
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Ingår i: New England Journal of Medicine. - 0028-4793. ; 371:26, s. 2488-2498
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Tidskriftsartikel (refereegranskat)abstract
- Background The incidence of hematologic cancers increases with age. These cancers are associated with recurrent somatic mutations in specific genes. We hypothesized that such mutations would be detectable in the blood of some persons who are not known to have hematologic disorders. Methods We analyzed whole-exome sequencing data from DNA in the peripheral-blood cells of 17,182 persons who were unselected for hematologic phenotypes. We looked for somatic mutations by identifying previously characterized single-nucleotide variants and small insertions or deletions in 160 genes that are recurrently mutated in hematologic cancers. The presence of mutations was analyzed for an association with hematologic phenotypes, survival, and cardiovascular events. Results Detectable somatic mutations were rare in persons younger than 40 years of age but rose appreciably in frequency with age. Among persons 70 to 79 years of age, 80 to 89 years of age, and 90 to 108 years of age, these clonal mutations were observed in 9.5% (219 of 2300 persons), 11.7% (37 of 317), and 18.4% (19 of 103), respectively. The majority of the variants occurred in three genes: DNMT3A, TET2, and ASXL1. The presence of a somatic mutation was associated with an increase in the risk of hematologic cancer (hazard ratio, 11.1; 95% confidence interval [CI], 3.9 to 32.6), an increase in all-cause mortality (hazard ratio, 1.4; 95% CI, 1.1 to 1.8), and increases in the risks of incident coronary heart disease (hazard ratio, 2.0; 95% CI, 1.2 to 3.4) and ischemic stroke (hazard ratio, 2.6; 95% CI, 1.4 to 4.8). Conclusions Age-related clonal hematopoiesis is a common condition that is associated with increases in the risk of hematologic cancer and in all-cause mortality, with the latter possibly due to an increased risk of cardiovascular disease. (Funded by the National Institutes of Health and others.).
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| 8. |
- Lange, Leslie A, et al.
(författare)
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Whole-Exome Sequencing Identifies Rare and Low-Frequency Coding Variants Associated with LDL Cholesterol.
- 2014
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297. ; 94:2, s. 233-245
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Tidskriftsartikel (refereegranskat)abstract
- Elevated low-density lipoprotein cholesterol (LDL-C) is a treatable, heritable risk factor for cardiovascular disease. Genome-wide association studies (GWASs) have identified 157 variants associated with lipid levels but are not well suited to assess the impact of rare and low-frequency variants. To determine whether rare or low-frequency coding variants are associated with LDL-C, we exome sequenced 2,005 individuals, including 554 individuals selected for extreme LDL-C (>98(th) or <2(nd) percentile). Follow-up analyses included sequencing of 1,302 additional individuals and genotype-based analysis of 52,221 individuals. We observed significant evidence of association between LDL-C and the burden of rare or low-frequency variants in PNPLA5, encoding a phospholipase-domain-containing protein, and both known and previously unidentified variants in PCSK9, LDLR and APOB, three known lipid-related genes. The effect sizes for the burden of rare variants for each associated gene were substantially higher than those observed for individual SNPs identified from GWASs. We replicated the PNPLA5 signal in an independent large-scale sequencing study of 2,084 individuals. In conclusion, this large whole-exome-sequencing study for LDL-C identified a gene not known to be implicated in LDL-C and provides unique insight into the design and analysis of similar experiments.
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