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Sökning: WFRF:(Manolescu Andrei)

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  • Amundadottir, Laufey T., et al. (författare)
  • A common variant associated with prostate cancer in European and African populations
  • 2006
  • Ingår i: Nature Genetics. - DeCODE Genet, IS-101 Reykjavik, Iceland. Univ Iceland, Landspitali Hosp, Dept Pathol, IS-101 Reykjavik, Iceland. Univ Iceland, Landspitali Hosp, Dept Urol, IS-101 Reykjavik, Iceland. Univ Michigan, Dept Human Genet, Ann Arbor, MI 48109 USA. Orebro Univ Hosp, Dept Urol & Clin Med, Orebro, Sweden. Karolinska Inst, Dept Med Epidemiol & Biostat, SE-17177 Stockholm, Sweden. Univ Michigan, Dept Urol, Ann Arbor, MI 48109 USA. Northwestern Univ, Feinberg Sch Med, Dept Urol, Chicago, IL 60611 USA. Washington Univ, Sch Med, Dept Psychiat, St Louis, MO 63110 USA. Univ Chicago, Dept Human Genet, Chicago, IL 60637 USA. Univ Michigan, Dept Internal Med, Ann Arbor, MI 48109 USA. : NATURE PUBLISHING GROUP. - 1061-4036 .- 1546-1718. ; 38:6, s. 652-658
  • Tidskriftsartikel (refereegranskat)abstract
    • With the increasing incidence of prostate cancer, identifying common genetic variants that confer risk of the disease is important. Here we report such a variant on chromosome 8q24, a region initially identified through a study of Icelandic families. Allele -8 of the microsatellite DG8S737 was associated with prostate cancer in three case-control series of European ancestry from Iceland, Sweden and the US. The estimated odds ratio (OR) of the allele is 1.62 (P = 2.7 x 10(-11)). About 19% of affected men and 13% of the general population carry at least one copy, yielding a population attributable risk (PAR) of approximately 8%. The association was also replicated in an African American case-control group with a similar OR, in which 41% of affected individuals and 30% of the population are carriers. This leads to a greater estimated PAR (16%) that may contribute to higher incidence of prostate cancer in African American men than in men of European ancestry.
  • Helgadottir, Anna, et al. (författare)
  • The same sequence variant on 9p21 associates with myocardial infarction, abdominal aortic aneurysm and intracranial aneurysm
  • 2008
  • Ingår i: Nature Genetics. - : Nature Publishing Group. - 1546-1718. ; 40:2, s. 217-224
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently, two common sequence variants on 9p21, tagged by rs10757278-G and rs10811661-T, were reported to be associated with coronary artery disease (CAD)(1-4) and type 2 diabetes (T2D)(5-7), respectively. We proceeded to further investigate the contributions of these variants to arterial diseases and T2D. Here we report that rs10757278-G is associated with, in addition to CAD, abdominal aortic aneurysm (AAA; odds ratio (OR) 1.31, P = 1.2 x 10(-12)) and intracranial aneurysm (OR = 1.29, P = 2.5 x 10(-6)), but not with T2D. This variant is the first to be described that affects the risk of AAA and intracranial aneurysm in many populations. The association of rs10811661-T to T2D replicates in our samples, but the variant does not associate with any of the five arterial diseases examined. These findings extend our insight into the role of the sequence variant tagged by rs10757278-G and show that it is not confined to atherosclerotic diseases.
  • Erlingsson, Sigurdur I., et al. (författare)
  • Reversal of Thermoelectric Current in Tubular Nanowires
  • 2017
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 119:3
  • Tidskriftsartikel (refereegranskat)abstract
    • We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign; i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector. The sign reversal can survive in the presence of impurities. We predict this result for core-shell nanowires, for uniform nanowires with surface states due to the Fermi level pinning, and for topological insulator nanowires.
  • Sultan, Muhammad Taha, et al. (författare)
  • Enhanced photoconductivity of SiGe nanocrystals in SiO2 driven by mild annealing
  • 2019
  • Ingår i: Applied Surface Science. - : ELSEVIER SCIENCE BV. - 0169-4332 .- 1873-5584. ; 469, s. 870-878
  • Tidskriftsartikel (refereegranskat)abstract
    • Photosensitive films based on finely dispersed semiconductor nanocrystals (NCs) in dielectric films have great potential for sensor applications. Here we report on preparation and characterization of photosensitive Si1-xGex NCs sandwiched between SiO2 matrix. A radio-frequency magnetron sputtering was applied to obtain a multilayer-structures (MLs) by depositing SiO2/SiGe/SiO2 films on Si (0 0 1) substrate. The Si1-xGex NCs were formed by a post-deposition annealing at 100-700 degrees C for 1-5 min. The effect of annealing temperature and time on MLs morphology and NCs size and density was studied using grazing incidence X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy and measurements of spectral distribution of photocurrent. It is demonstrated how the photoconductive properties of the MLs can be enhanced and tailored by controlling the NCs formation conditions and the presence of stress field in MLs and defects acting as traps and recombination centers. All these features can be adjusted/controlled by altering the annealing conditions (temperature and time). The MLs photosensitivity was increased of more than an order of magnitude by the annealing process. A mechanism, where a competition between crystallization process (NCs formation and evolution i.e. size and shapes) and stress field appearance determines the peak position in the photocurrent spectra, was identified.
  • Sultan, Muhammad Taha, et al. (författare)
  • Fabrication and characterization of Si1-xGex nanocrystals in as-grown and annealed structures : a comparative study
  • 2019
  • Ingår i: Beilstein Journal of Nanotechnology. - : BEILSTEIN-INSTITUT. - 2190-4286. ; 10, s. 1873-1882
  • Tidskriftsartikel (refereegranskat)abstract
    • Multilayer structures comprising of SiO2/SiGe/SiO2 and containing SiGe nanoparticles were obtained by depositing SiO2 layers using reactive direct current magnetron sputtering (dcMS), whereas, Si and Ge were co-sputtered using dcMS and high-power impulse magnetron sputtering (HiPIMS). The as-grown structures subsequently underwent rapid thermal annealing (550-900 degrees C for 1 min) in N-2 ambient atmosphere. The structures were investigated using X-ray diffraction, high-resolution transmission electron microscopy together with spectral photocurrent measurements, to explore structural changes and corresponding properties. It is observed that the employment of HiPIMS facilitates the formation of SiGe nanoparticles (2.1 +/- 0.8 nm) in the as-grown structure, and that presence of such nanoparticles acts as a seed for heterogeneous nucleation, which upon annealing results in the periodically arranged columnar self-assembly of SiGe core-shell nanocrystals. An increase in photocurrent intensity by more than an order of magnitude was achieved by annealing. Furthermore, a detailed discussion is provided on strain development within the structures, the consequential interface characteristics and its effect on the photocurrent spectra.
  • Sultan, Muhammad Taha, et al. (författare)
  • Structural and photoluminescence study of TiO2 layer with self-assembled Si1-xGex nanoislands
  • 2020
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 128:8
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the surface morphology and growth process of SiGe nanoislands on TiO2 films, deposited over Si (001) substrates by high power impulse magnetron sputtering, followed by varying annealing parameters (i.e., 500-750 degrees C for 30min to 20h). Structural analysis was performed by atomic force microscopy, scanning electron microscopy, and grazing incidence x-ray diffraction. Two structural schemes were taken into consideration, i.e., SiGe grown over pre-annealed TiO2 (scheme I) and as-grown TiO2 (scheme II). Photoluminescence (PL) study of the structures revealed spectral features comprised of multiple peak features related to localized and surface states within the oxide layer, along with a peak due to the SiGe nano-islands. It was observed that the spectral feature and intensity depend on the surface morphology and the crystallinity of the underlying TiO2 layer. The structures were subjected to low temperature PL measurements, and the spectra were de-convoluted in order to validate the origin of the obtained spectra. Structural analysis revealed that pre-annealing the underlying polycrystalline TiO2 film, prior to deposition of SiGe layers (scheme I), facilitates the formation of SiGe nanoislands, preferably along the grain boundaries (due to their higher interfacial energy). In comparison, for the case of SiGe deposited over as-grown TiO2 (scheme II), annealing of the structure resulted in random distribution of nanoislands across the entire film. The size of the nanoislands grew with increased annealing time up until the point they started to coalesce, forming discontinuous SiGe layers and eventually leading to melting of the layer.
  • Thorgeirsson, Thorgeir E, et al. (författare)
  • A variant associated with nicotine dependence, lung cancer and peripheral arterial disease
  • 2008
  • Ingår i: Nature. - : Nature Publishing Group. - 0028-0836. ; 452:7187, s. 9-638
  • Tidskriftsartikel (refereegranskat)abstract
    • Smoking is a leading cause of preventable death, causing about 5 million premature deaths worldwide each year(1,2). Evidence for genetic influence on smoking behaviour and nicotine dependence (ND)(3-8) has prompted a search for susceptibility genes. Furthermore, assessing the impact of sequence variants on smoking-related diseases is important to public health(9,10). Smoking is the major risk factor for lung cancer (LC)(11-14) and is one of the main risk factors for peripheral arterial disease (PAD)(15-17). Here we identify a common variant in the nicotinic acetylcholine receptor gene cluster on chromosome 15q24 with an effect on smoking quantity, ND and the risk of two smoking- related diseases in populations of European descent. The variant has an effect on the number of cigarettes smoked per day in our sample of smokers. The same variant was associated with ND in a previous genomewide association study that used low- quantity smokers as controls(18,19), and with a similar approach we observe a highly significant association with ND. A comparison of cases of LC and PAD with population controls each showed that the variant confers risk of LC and PAD. The findings provide a case study of a gene - environment interaction(20), highlighting the role of nicotine addiction in the pathology of other serious diseases.
  • Wesslén, Carl, 1988- (författare)
  • Confinement Sensitivity in Quantum Dot Spin Relaxation
  • 2017
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Quantum dots, also known as artificial atoms, are created by tightly confining electrons, and thereby quantizing their energies. They are important components in the emerging fields of nanotechnology where their potential uses vary from dyes to quantum computing qubits. Interesting properties to investigate are e.g. the existence of atom-like shell structures and lifetimes of prepared states.Stability and controllability are important properties in finding applications to quantum dots. The ability to prepare a state and change it in a controlled manner without it loosing coherence is very useful, and in some semiconductor quantum dots, lifetimes of up to several milliseconds have been realized. Here we focus on dots in semiconductor materials and investigate how the confined electrons are effected by their experienced potential.The shape of the dot will effect its properties, and is important when considering a suitable model. Structures elongated in one dimension, often called nanowires, or shaped as rings have more one-dimensional characteristics than completely round or square dots. The two-dimensional dots investigated here are usually modeled as harmonic oscillators, however we will also consider circular well models.The effective potential confining the electrons is investigated both in regard to how elliptical it is, as well as how results differ when using a harmonic oscillator or a circular well potential. By mixing spin states through spin-orbit interaction transitioning between singlet and triplet states becomes possible with spin independent processes such as phonon relaxation. We solve the spin-mixing two-electron problem numerically for some confinement, and calculate the phonon transition rate between the lowest energy singlet and triplet states using Fermi's golden rule.The strength of the spin-orbit interaction is varied both by changing the coupling constants, and by applying an external, tilted, magnetic field. The relation between magnetic field parameters and dot parameters are used to maximize state lifetimes, and to model experimental results.
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