| 1. |
- Forsberg, Lars A., et al.
(författare)
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Age-related somatic structural changes in the nuclear genome of human blood cells
- 2012
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Ingår i: American Journal of Human Genetics. - : Elsevier BV. - 0002-9297 .- 1537-6605. ; 90:2, s. 217-228
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Tidskriftsartikel (refereegranskat)abstract
- Structural variations are among the most frequent interindividual genetic differences in the human genome. The frequency and distribution of de novo somatic structural variants in normal cells is, however, poorly explored. Using age-stratified cohorts of 318 monozygotic (MZ) twins and 296 single-born subjects, we describe age-related accumulation of copy-number variation in the nuclear genomes in vivo and frequency changes for both megabase- and kilobase-range variants. Megabase-range aberrations were found in 3.4% (9 of 264) of subjects ≥60 years old; these subjects included 78 MZ twin pairs and 108 single-born individuals. No such findings were observed in 81 MZ pairs or 180 single-born subjects who were ≤55 years old. Recurrent region- and gene-specific mutations, mostly deletions, were observed. Longitudinal analyses of 43 subjects whose data were collected 7-19 years apart suggest considerable variation in the rate of accumulation of clones carrying structural changes. Furthermore, the longitudinal analysis of individuals with structural aberrations suggests that there is a natural self-removal of aberrant cell clones from peripheral blood. In three healthy subjects, we detected somatic aberrations characteristic of patients with myelodysplastic syndrome. The recurrent rearrangements uncovered here are candidates for common age-related defects in human blood cells. We anticipate that extension of these results will allow determination of the genetic age of different somatic-cell lineages and estimation of possible individual differences between genetic and chronological age. Our work might also help to explain the cause of an age-related reduction in the number of cell clones in the blood; such a reduction is one of the hallmarks of immunosenescence.
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| 2. |
- Naghavi, N., et al.
(författare)
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Buffer layers and transparent conducting oxides for chalcopyrite Cu(In,Ga)(S,Se)(2) based thin film photovoltaics : Present status and current developments
- 2010
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Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 18:6, s. 411-433
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present contribution is to give a review on the recent work concerning Cd-free buffer and window layers in chalcopyrite solar cells using various deposition techniques as well as on their adaptation to chalcopyrite-type absorbers such as Cu(In,Ga)Se-2, CuInS2, or Cu(In,Ga)(S,Se)(2). The corresponding solar-cell performances, the expected technological problems, and current attempts for their commercialization will be discussed. The most important deposition techniques developed in this paper are chemical bath deposition, atomic layer deposition, ILGAR deposition, evaporation, and spray deposition. These deposition methods were employed essentially for buffers based on the following three materials: In2S3, ZnS, Zn1-xMgxO.
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| 3. |
- Pinto, H., et al.
(författare)
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First-principles studies of the effect of (001) surface terminations on the electronic properties of the negatively charged nitrogen-vacancy defect in diamond
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:4
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Tidskriftsartikel (refereegranskat)abstract
- Density functional calculations have been carried out on (001)-orientated slabs of diamond with different surface terminations. A negatively charged nitrogen-vacancy defect (NV-) is placed in the middle of the slab approximately 1 nm from each surface and the effect of the surface on the internal optical transition in NV- investigated. The calculations show that the chemical nature of the surface is important. We find that although the clean surface does not lead to charge transfer between the defect and the surface, there is a splitting of the empty excited state, the final state in optical absorption, arising from a strong hybridization of the surface and defect bands. This leads to a broadening of the 1.945-eV transition of the NV- defect. OH- and F-terminated surfaces have no surface states in the band gap and again charge transfer between the defect and surface does not occur. The splitting of the e levels responsible for the optical transitions for OH or F termination is similar to that found in periodic boundary condition simulations for bulk diamond where the defects are separated by 1 nm, and thus the calculations show that hydroxylated or fluorinated surfaces give favorable optical properties.
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| 4. |
- Tiwari, Amit K., et al.
(författare)
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Calculated electron affinity and stability of halogen-terminated diamond
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:24
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Tidskriftsartikel (refereegranskat)abstract
- The chemical termination of diamond has a dramatic impact on its electrical and chemical properties, where hydrogen and oxygen termination produce negative and positive electron affinities, respectively. However, the impact of halogen termination is not fully understood. We show that for low-index surfaces, 100% fluorinated surfaces exhibit chemically stable positive electron affinities in the 1.17 to 2.63 eV range, whereas 100% chlorination is energetically unfavorable. At lower coverage the positive electron affinity is smaller, being a combination of halogen-terminated and unterminated sites. For mixed halogen and hydrogen termination, a wide range of negative and positive electron affinities can be achieved by varying the relative concentrations of adsorbed species.
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| 5. |
- Tiwari, Amit K., et al.
(författare)
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Thermodynamic stability and electronic properties of F- and Cl-terminated diamond
- 2012
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 209:9, s. 1709-1714
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Tidskriftsartikel (refereegranskat)abstract
- The chemical termination of diamond has important consequences for its electrical and chemical properties. Despite the impressive potential for various scientific and technological applications, halogen termination of diamond is not fully understood. We find using first principle atomistic simulation that 100% fluorinated diamond (100) surface exhibit a chemically stable positive electron affinity of 2.13 eV, whereas 100% chlorination is energetically unfavourable. The positive electron affinity of halogenated diamond generally increases with increasing surface coverage. For mixed halogen and hydrogen termination, a wide range of negative and positive electron affinities can be achieved theoretically by varying the relative concentrations of adsorbed species.
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| 6. |
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| 7. |
- Rai, Radheshyam, et al.
(författare)
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Experimental Techniques: An Introductory Overview
- 2012
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Ingår i: Synthesis, Characterization and Application of Smart Materials. - USA : Nova Science Publishers, Inc.. - 9781614706427 ; , s. 15-30
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Smart materials, one of the more focused points in materials research, deal primarily with the chemistry, physics and applications of materials in the real world because it induces conformational changes in complex structures and properties which are useful for the control of them. The thrust area of these types of materials are the combination of functional properties like thermal, electric, magnetic, superconducting and optical, which have led to the development of a wide range of new technological devices. These types of materials have been found to be very useful and interesting for various solid state devices. This book examines research developments of smart materials, including processing, properties and applications, which include device materials and environmentally friendly materials. (Imprint: Nova)
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| 8. |
- Shukla, S. K., et al.
(författare)
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Fabrication of a tunable glucose biosensor based on zinc oxide/chitosan-graft-poly (vinyl alcohol) core-shell nanocomposite
- 2012
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Ingår i: Talanta. - : Elsevier. - 0039-9140. ; 99, s. 283-287
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Tidskriftsartikel (refereegranskat)abstract
- A potentiometrically tuned-glucose biosensor was fabricated using core-shell nanocomposite based on zinc oxide encapsulated chitosan-graft-poly(vinyl alcohol) (ZnO/CHIT-g-PVAL). In a typical experiment, ZnO/CHIT-g-PVAL core-shell nanocomposite containing <20 nm ZnO nanoparticles was synthesized using wet-chemical method. The glucose responsive bio-electrode, i.e., glucose oxidase/ZnO/chitosan-graft-poly(vinyl alcohol) (GOD/ZnO/CHIT-g-PVAL/ITO) was obtained by immobilization of glucose oxidase (GOD) onto the electrode made of resulting ZnO core-shell nanocomposite coated on the indium-tin oxide (ITO) glass substrate. The ZnO/CHIT-g-PVAL/ITO and GOD/ZnO/CHIT-g-PVAL electrodes were characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), whereas ZnO/CHIT-g-PVAL size of core-shell nanoparticles were measured using transmission electron microscopy (TEM). The electrostatic interaction between GOD and ZnO/CHIT-g-PVAL provided the resulting tuned enzyme electrode with a high degree of enzyme immobilization and excellent lifetime stability. The response studies were carried out as a function of glucose concentration with potentiometric measurement. The GOD/ZnO/CHIT-g-PVAL/ITO bioelectrode has showed a linear potential response to the glucose concentration ranging from 2 mu M to 1.2 mM. The glucose biosensor exhibited a fast surface-controlled redox biochemistry with a detection limit of 0.2 mu M, a sensitivity of >0.04 V/mu M and a response time of three sec. ZnO/CHIT-g-PVAL core-shell nanocomposite could be a promising nanomaterials for a range of enzymic biosensors.
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| 9. |
- Tiwari, Ashutosh, et al.
(författare)
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Bionanomaterials for Emerging Biosensors Technology
- 2012
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Ingår i: Synthesis, Characterization and Application of Smart Materials. - USA : Nova Science Publishers, Inc.. - 9781614706427 ; , s. 137-154
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Smart materials, one of the more focused points in materials research, deal primarily with the chemistry, physics and applications of materials in the real world because it induces conformational changes in complex structures and properties which are useful for the control of them. The thrust area of these types of materials are the combination of functional properties like thermal, electric, magnetic, superconducting and optical, which have led to the development of a wide range of new technological devices. These types of materials have been found to be very useful and interesting for various solid state devices. This book examines research developments of smart materials, including processing, properties and applications, which include device materials and environmentally friendly materials
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| 10. |
- Tiwari, Amit K., et al.
(författare)
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Bromine functionalisation of diamond : an ab initio study
- 2012
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Ingår i: Physica Status Solidi (a) applications and materials science. - : Wiley. - 1862-6300 .- 1862-6319. ; 209:9, s. 1703-1708
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Tidskriftsartikel (refereegranskat)abstract
- Immobilisation of organic molecules on diamond surfaces is of great interest for biomedical applications. While H, F and Cl terminations, as a linker, have been studied extensively, the bromination of diamond is not fully understood. We have performed ab initio simulations to investigate the chemisorption of Br onto C- and H-terminated diamond (100) surfaces. We find that due to steric interaction, 100% surface coverage of Br is not stable, however, surface coverage up to around 50% is theoretically achievable. The chemisorption energies corresponding to lower surface coverages of Br are found comparable to those of hydrogen. Partial surface coverages (25 and 50%) of Br on C-terminated diamond exhibit nearly equal positive electron affinities of 0.45 and 0.52 eV, respectively. Addition of hydrogen reduces the electron affinity and for 25% of Br on an otherwise H-terminated surface, a negative electron affinity of 0.57 eV is calculated.
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