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Sökning: WFRF:(Janusz M) > (2010-2014)

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1.
  • Adlarson, Patrik, et al. (författare)
  • Abashian-Booth-Crowe Effect in Basic Double-Pionic Fusion : A New Resonance?
  • 2011
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:24, s. 242302-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on an exclusive and kinematically complete high-statistics measurement of the basic double-pionic fusion reaction pn -> d pi(0)pi(0) over the full energy region of the ABC effect, a pronounced low-mass enhancement in the pi pi-invariant mass spectrum. The measurements, which cover also the transition region to the conventional t- channel Delta Delta process, were performed with the upgraded WASA detector setup at COSY. The data reveal the Abashian-Booth-Crowe effect to be uniquely correlated with a Lorentzian energy dependence in the integral cross section. The observables are consistent with a narrow resonance with m = 2.37 GeV, Gamma approximate to 70 MeV and I(J(P)) = 0(3(+)) in both pn and Delta Delta systems. Necessary further tests of the resonance interpretation are discussed.
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2.
  • Adlarson, Patrik, et al. (författare)
  • Evidence for a New Resonance from Polarized Neutron-Proton Scattering
  • 2014
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:20, s. 202301-
  • Tidskriftsartikel (refereegranskat)abstract
    • Exclusive and kinematically complete high-statistics measurements of quasifree polarized (n) over right arrowp scattering have been performed in the energy region of the narrow resonancelike structure d* with I(J(P)) = 0(3(+)),M approximate to 2380 MeV, and Gamma approximate to 70 MeV observed recently in the double-pionic fusion channels pn -> d pi(0)pi(0) and pn -> d pi(+)pi(-). The experiment was carried out with the WASA detector setup at COSY having a polarized deuteron beam impinged on the hydrogen pellet target and utilizing the quasifree process (d) over right arrowp -> np + p(spectator). This allowed the np analyzing power, A(y), to be measured over a broad angular range. The obtained A(y) angular distributions deviate systematically from the current SAID SP07 NN partial-wave solution. Incorporating the new A(y) data into the SAID analysis produces a pole in the D-3(3) - (3)G(3) waves in support of the d* resonance hypothesis.
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3.
  • Adlarson, Patrik, et al. (författare)
  • pi(0)pi(0) Production in proton-proton collisions at T-p=1.4 GeV The WASA-at-COSY Collaboration
  • 2012
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 706:4-5, s. 256-262
  • Tidskriftsartikel (refereegranskat)abstract
    • The reaction pp -> pp pi(0)pi(0) has been investigated at a beam energy of 1.4 GeV using the WASA-at-COSY facility. The total cross section is found to be (324 +/- 21(systematic) +/- 58(normalization)) mu b. In order to study the production mechanism, differential kinematic distributions have been evaluated. The differential distributions indicate that both initial state protons are excited into intermediate Delta(1232) resonances, each decaying into a proton and a single pion, thereby producing the pion pair in the final state. No significant contribution of the Roper resonance N*(1440) via its decay into a proton and two pions is found.
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4.
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5.
  • Lang, J. J. K., et al. (författare)
  • Tin-stabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
  • 2011
  • Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 605:9-10, s. 883-888
  • Tidskriftsartikel (refereegranskat)abstract
    • Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of Sn-III dimers. Furthermore, a new Sn-induced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.
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6.
  • Laukkanen, P., et al. (författare)
  • Ultrathin (1x2)-Sn layer on GaAs(100) and InAs(100) substrates : A catalyst for removal of amorphous surface oxides
  • 2011
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:23, s. 231908-1-231908-3
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous surface oxides of III-V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs(100) and InAs(100) surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure results in the initial well-defined Sn-stabilized (1x2) surface even for samples exposed to air for a prolonged time. Based on ab initio calculations we propose that the phenomenon is due to indirect and direct effects of Sn. The Sn-induced surface composition weakens oxygen adsorption.
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7.
  • Laukkanen, P., et al. (författare)
  • Bismuth-stabilized c(2X6) reconstruction on a InSb(100) substrate : Violation of the electron counting model
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X .- 2469-9950 .- 2469-9969. ; 81:3
  • Tidskriftsartikel (refereegranskat)abstract
    • By means of scanning tunneling microscopy/spectroscopy (STM/STS), photoelectron spectroscopy, and first-principles calculations, we have studied the bismuth (Bi) adsorbate-stabilized InSb(100) substrate surface which shows a c(2X6) low-energy electron diffraction pattern [thus labeled Bi/InSb(100)c(2X6) surface] and which includes areas with metallic STS curves as well as areas with semiconducting STS curves. The first-principles phase diagram of the Bi/InSb(100) surface demonstrates the presence of the Bi-stabilized metallic c(2X6) reconstruction and semiconducting (4X3) reconstruction depending on the chemical potentials, in good agreement with STS results. The existence of the metallic c(2X6) phase, which does not obey the electron counting model, is attributed to the partial prohibition of the relaxation in the direction perpendicular to dimer rows in the competing reconstructions and the peculiar stability of the Bi-stabilized dimer rows. Based on (i) first-principles phase diagram, (ii) STS results, and (iii) comparison of the measured and calculated STM and photoemission data, we show that the measured Bi/InSb(100)c(2X6) surface includes metallic areas with the stable c(2X6) atomic structure and semiconducting areas with the stable (4X3) atomic structure.
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8.
  • Laukkanen, P., et al. (författare)
  • Core-level shifts of the c(8 x 2)-reconstructed InAs(100) and InSb(100) surfaces
  • 2010
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 177:1, s. 52-57
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied In-stabilized c(8 2)-reconstructed InAs(1 0 0) and InSb(1 0 0) semiconductor surfaces, which play a key role in growing improved III-V interfaces for electronics devices, by core-level photoelectron spectroscopy and first-principles calculations. The calculated surface core-level shifts (SCLSs) for the zeta and zeta a models, which have been previously established to describe the atomic structures of the III-V(1 00)c(8 x 2) surfaces, yield hitherto not reported interpretation for the As 3d, In 4d, and Sb 4d core-level spectra of the III-V(1 00)c(8 x 2) surfaces, concerning the number and origins of SCLSs. The fitting analysis of the measured spectra with the calculated zeta and zeta a SCLS values shows that the InSb spectra are reproduced by the zeta SCLSs better than by the zeta a SCLSs. Interestingly, the zeta a fits agree better with the InAs spectra than the zeta fits do, indicating that the zeta a model describes the InAs surface better than the InSb surface. These results are in agreement with previous X-ray diffraction data. Furthermore, an introduction of the complete-screening model, which includes both the initial and final state effects, does not improve the fitting of the InSb spectra, proposing the suitability of the initial-state model for the SCLSs of the III-V(1 0 0)c(8 x 2) surfaces. The found SCLSs are discussed with the ab initio on-site charges.
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9.
  • Punkkinen, Marko Patrick John, et al. (författare)
  • Oxidized In-containing III-V(100) surfaces : Formation of crystalline oxide films and semiconductor-oxide interfaces
  • 2011
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:19, s. 195329-
  • Tidskriftsartikel (refereegranskat)abstract
    • Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinning, which opens up new possibilities to develop long-sought III-V metal-oxide-semiconductor transistors. Calculations reveal that the early stages in the oxidation process include only O-III bonds due to the geometry of the III-V(100)c(8 x 2) substrate, which is responsible for the formation of the ordered interface. The found surfaces provide a different platform to study the oxidation and properties of oxides, e. g., the origins of the photoemission shifts and electronic structures, using surface science methods.
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10.
  • Bellenguez, Celine, et al. (författare)
  • Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke
  • 2012
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 44:3, s. 141-328
  • Tidskriftsartikel (refereegranskat)abstract
    • Genetic factors have been implicated in stroke risk, but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) for ischemic stroke and its subtypes in 3,548 affected individuals and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 affected individuals and 6,281 controls. We replicated previous associations for cardioembolic stroke near PITX2 and ZFHX3 and for large vessel stroke at a 9p21 locus. We identified a new association for large vessel stroke within HDAC9 (encoding histone deacetylase 9) on chromosome 7p21.1 (including further replication in an additional 735 affected individuals and 28,583 controls) (rs11984041; combined P = 1.87 x 10(-11); odds ratio (OR) = 1.42, 95% confidence interval (CI) = 1.28-1.57). All four loci exhibited evidence for heterogeneity of effect across the stroke subtypes, with some and possibly all affecting risk for only one subtype. This suggests distinct genetic architectures for different stroke subtypes.
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11.
  • Guziewicz, E., et al. (författare)
  • Synchrotron photoemission study of (Zn,Co)O films with uniform Co distribution
  • 2011
  • Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1046-1050
  • Konferensbidrag (refereegranskat)abstract
    • We present results of a resonant photoemission study of (Zn,Co)O films with Co content between 2% and 7%. The films were grown by Atomic Layer Deposition (ALD) at low temperature of 160 degrees C and show fully paramagnetic behavior. The Co ions are uniformly distributed in the ZnO matrix and are free of foreign phases and metal accumulations as indicated by TEM data. The electronic structure of (Zn,Co)O films was studied by Resonant Photoemission Spectroscopy across the Co3p-Co3d photoionization threshold. We have observed that the resonant enhancement of the photoemission intensity from the Co3d shell is not the same for samples with different cobalt content. We suggest that the Co3d contribution to the valence band depends on both Co and H content. (C) 2011 Elsevier Ltd. All rights reserved.
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12.
  • Sawcer, Stephen, et al. (författare)
  • Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis
  • 2011
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 476:7359, s. 214-219
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis.
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13.
  • Su, Zhan, et al. (författare)
  • Common variants at the MHC locus and at chromosome 16q24.1 predispose to Barrett's esophagus.
  • 2012
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 44:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Barrett's esophagus is an increasingly common disease that is strongly associated with reflux of stomach acid and usually a hiatus hernia, and it strongly predisposes to esophageal adenocarcinoma (EAC), a tumor with a very poor prognosis. We report the first genome-wide association study on Barrett's esophagus, comprising 1,852 UK cases and 5,172 UK controls in the discovery stage and 5,986 cases and 12,825 controls in the replication stage. Variants at two loci were associated with disease risk: chromosome 6p21, rs9257809 (Pcombined=4.09×10(-9); odds ratio (OR)=1.21, 95% confidence interval (CI)=1.13-1.28), within the major histocompatibility complex locus, and chromosome 16q24, rs9936833 (Pcombined=2.74×10(-10); OR=1.14, 95% CI=1.10-1.19), for which the closest protein-coding gene is FOXF1, which is implicated in esophageal development and structure. We found evidence that many common variants of small effect contribute to genetic susceptibility to Barrett's esophagus and that SNP alleles predisposing to obesity also increase risk for Barrett's esophagus.
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14.
  • Bateman, Alex, et al. (författare)
  • RNAcentral: A vision for an international database of RNA sequences.
  • 2011
  • Ingår i: RNA (New York, N.Y.). - : Cold Spring Harbor Laboratory. - 1469-9001 .- 1355-8382. ; 17:11, s. 1941-6
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last decade there has been a great increase in the number of noncoding RNA genes identified, including new classes such as microRNAs and piRNAs. There is also a large growth in the amount of experimental characterization of these RNA components. Despite this growth in information, it is still difficult for researchers to access RNA data, because key data resources for noncoding RNAs have not yet been created. The most pressing omission is the lack of a comprehensive RNA sequence database, much like UniProt, which provides a comprehensive set of protein knowledge. In this article we propose the creation of a new open public resource that we term RNAcentral, which will contain a comprehensive collection of RNA sequences and fill an important gap in the provision of biomedical databases. We envision RNA researchers from all over the world joining a federated RNAcentral network, contributing specialized knowledge and databases. RNAcentral would centralize key data that are currently held across a variety of databases, allowing researchers instant access to a single, unified resource. This resource would facilitate the next generation of RNA research and help drive further discoveries, including those that improve food production and human and animal health. We encourage additional RNA database resources and research groups to join this effort. We aim to obtain international network funding to further this endeavor.
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15.
  • Cruz, Jose Almeida, et al. (författare)
  • RNA-Puzzles : A CASP-like evaluation of RNA three-dimensional structure prediction
  • 2012
  • Ingår i: RNA. - : Cold Spring Harbor Laboratory. - 1355-8382 .- 1469-9001. ; 18:4, s. 610-625
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the results of a first, collective, blind experiment in RNA three-dimensional (3D) structure prediction, encompassing three prediction puzzles. The goals are to assess the leading edge of RNA structure prediction techniques; compare existing methods and tools; and evaluate their relative strengths, weaknesses, and limitations in terms of sequence length and structural complexity. The results should give potential users insight into the suitability of available methods for different applications and facilitate efforts in the RNA structure prediction community in ongoing efforts to improve prediction tools. We also report the creation of an automated evaluation pipeline to facilitate the analysis of future RNA structure prediction exercises.
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16.
  • Di Marco, I., et al. (författare)
  • Electron correlations in Mn(x)Ga(1–x)As as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 4, s. 6-2645
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
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17.
  • Dziawa, P., et al. (författare)
  • Defect Free PbTe Nanowires Grown by Molecular Beam Epitaxy on GaAs(111)B Substrates
  • 2010
  • Ingår i: Crystal Growth & Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 10:1, s. 109-113
  • Tidskriftsartikel (refereegranskat)abstract
    • The molecular beam epitaxial growth of PbTe nanowires oil GaAs(111)B substrates is reported. The growth process was based oil the Au-catalyzed vapor-liquid-solid mechanism. These nanowires grow along the [100] axis; they are perpendicular to the substrate, have tapered shapes, and have diameters of about 90 rim at the base and 60 run at the top. High resolution transmission electron microscopy pictures reveal that the PbTe nanowires have a rock-salt structure and, in contrast to the one-dimensional structures of III-V and II-VI compound semiconductors such as GaAs. InAs, or ZnTe, are free from stacking faults. A theoretical analysis of these experimental findings, which is based oil ab initio modeling of the PbTe nanowires, is also presented.
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18.
  • Gluba, L., et al. (författare)
  • On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E-1 and E-1 + Delta(1) optical transitions
  • 2014
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The dilute (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. In this paper, we verify the ellipsometric results and compare them with more precise photoreflectance method, which gives an important insight into the interaction of the Mn-related states with the ones of GaAs valence band. No spectral shifts observed for the E-1 and E-1 + Delta(1) interband transitions in highly doped and annealed (Ga,Mn)As epitaxial layers indicate that the coupling between a detached Mn impurity band and the valence band does not occur. Our findings are supported by the characterizations of the (Ga,Mn)As epitaxial layers with the high resolution transmission electron microscopy and magnetization measurements. (c) 2014 AIP Publishing LLC.
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19.
  • Gryglas-Borysiewicz, M., et al. (författare)
  • Hydrostatic pressure study of the paramagnetic-ferromagnetic phase transition in (Ga,Mn)As
  • 2010
  • Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 82:15
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of hydrostatic pressure on the paramagnetic-ferromagnetic phase transition has been studied in (Ga,Mn)As. The variation in the Curie temperature (T-C) with pressure was monitored by two transport methods: (1) measurement of zero-field resistivity versus temperature rho(T) and (2) dependence on temperature of the Hall voltage hysteresis loop. Two specimens of different resistivity characteristics were examined. The measured pressure-induced changes in T-C were relatively small (on the order of 1 K/GPa) for both samples, however they were opposite for the two.
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20.
  • Gutowski, M. W., et al. (författare)
  • Interval Identification of FMR Parameters for Spin Reorientation Transition in (Ga,Mn)As
  • 2012
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 121:5-6, s. 1228-1230
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we report results of ferromagnetic resonance studies of a 6% 15 nm (Ga,Mn)As layer, deposited on (001)-oriented GaAs. The measurements were performed with in-plane oriented magnetic field, in the temperature range between 5 K and 120 K. We observe a temperature induced reorientation of the effective in-plane easy axis from [(1) over bar 10] to [110] direction close to the Curie temperature. The behavior of magnetization is described by anisotropy fields, H-eff (= 4 pi M - H-2 perpendicular to), H-2 parallel to, and H-4 parallel to. In order to precisely investigate this reorientation, numerical values of anisotropy fields have been determined using powerful - but still largely unknown - interval calculations. In simulation mode this approach makes possible to find all the resonance fields for arbitrarily oriented sample, which is generally intractable analytically. In "fitting" mode we effectively utilize full experimental information, not only those measurements performed in special, distinguished directions, to reliably estimate the values of important physical parameters as well as their uncertainties and correlations.
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21.
  • Kamara, S., et al. (författare)
  • In-Plane Magnetic Anisotropy and Temperature Dependence of Switching Field in (Ga, Mn)As Ferromagnetic Semiconductors
  • 2012
  • Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 12:6, s. 4868-4873
  • Tidskriftsartikel (refereegranskat)abstract
    • We explore the magnetic anisotropy of GaMnAs ferromagnetic semiconductor by Planar Hall Effect (PHE) measurements. Using low magnitude of applied magnetic field (i.e., when the magnitude H is smaller than both cubic Hc and uniaxial Hu anisotropy field), we have observed various shapes of applied magnetic field direction dependence of Planar Hall Resistance (PHR). In particular, in two regions of temperature. At T TC/2 the “zigzag-shape” signal of PHR. They reflect different magnetic anisotropy and provide information about magnetization reversal process in GaMnAs ferromagnetic semiconductor. The theoretical model calculation of PHR based on the free energy density reproduces well the experimental data. We report also the temperature dependence of anisotropy constants and magnetization orientations. The transition of easy axis from biaxial to uniaxiale axes has been observed and confirmed by SQUID measurements.
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22.
  • Laukkanen, P., et al. (författare)
  • Bismuth-containing c(4 x 4) surface structure of the GaAs(100) studied by synchrotron-radiation photoelectron spectroscopy and ab initio calculations
  • 2014
  • Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 193, s. 34-38
  • Tidskriftsartikel (refereegranskat)abstract
    • Bismuth (Bi) induced c(4 x 4) surface structure of the GaAs(1 0 0) substrate, i.e., the GaAs(1 0 0)c(4 x 4)-Bi surface has been studied with synchrotron-radiation photoelectron spectroscopy and ab initio calculations. The surface was prepared by combining molecular beam epitaxy and in situ electron diffraction methods, and then the sample was transferred to a photoemission chamber without breaking ultrahigh vacuum conditions. Calculations show that the c(4 x 4)13 type unit cells, which consist of Bi-Bi and Bi-As dimers, are energetically favored on the surface and that Bi atoms occupy only the topmost atomic sites bonding to the As layer below. The presence of the c(4 x 4)(3 structure is supported by the comparison of measured and calculated core-level shifts of the GaAs(1 00)c(4 x 4)-Bi surface. Simulated scanning-tunneling-microscopy (STM) images, based on the suggested models, are presented for the comparison with future STM measurements. (C) 2014 Elsevier B.V. All rights reserved.
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23.
  • Niu, Shuli, et al. (författare)
  • Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms.
  • 2012
  • Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 194:3, s. 775-783
  • Tidskriftsartikel (refereegranskat)abstract
    • • It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. • Here, we compiled data from 169 globally distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem-level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. • We found that the temperature response of NEE followed a peak curve, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum temperature) rather than changes in the temperature sensitivity of ecosystem respiration. • Ecosystem-level thermal optimality is a newly revealed ecosystem property, presumably reflecting associated evolutionary adaptation of organisms within ecosystems, and has the potential to significantly regulate ecosystem-climate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models.
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24.
  • Proselkov, O., et al. (författare)
  • Thickness dependent magnetic properties of (Ga,Mn) As ultrathin films
  • 2012
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:26
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a monotonic reduction of Curie temperature in dilute ferromagnetic semiconductor (Ga,Mn) As upon a well controlled chemical-etching/oxidizing thinning from 15 nm down to complete removal of the ferromagnetic response. The effect already starts at the very beginning of the thinning process and is accompanied by the spin reorientation transition of the in-plane uniaxial anisotropy. We postulate that a negative gradient along the growth direction of self-compensating defects (Mn interstitial) and the presence of surface donor traps gives quantitative account on these effects within the p-d mean field Zener model with adequate modifications to take a nonuniform distribution of holes and Mn cations into account. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731202]
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25.
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26.
  • Werner, H M J, et al. (författare)
  • A discordant histological risk classification in preoperative and operative biopsy in endometrial cancer is reflected in metastatic risk and prognosis.
  • 2013
  • Ingår i: European Journal of Cancer. - : Elsevier BV. - 0959-8049. ; 49:3, s. 625-632
  • Tidskriftsartikel (refereegranskat)abstract
    • INTRODUCTION: In endometrial cancer, tissue for histological evaluation is obtained preoperatively (endometrial biopsy) and operatively (hysterectomy specimen). We investigated if a discordant risk classification based on preoperative and operative biopsy is reflected in metastatic risk and prognosis. PATIENTS AND METHODS: One thousand three hundred and seventy-four patients were prospectively included in a multicentre setting (Molecular Markers for Treatment of Endometrial Cancer (MoMaTEC) study). Preoperative and operative specimens were classified as high risk if non-endometrioid histology or endometrioid grade 3; otherwise low risk. Disease specific survival differences were calculated by means of Kaplan-Meier and Cox proportional hazard models. RESULTS: Discordant risk was found in 207 (16%) cases. Lymph node metastases were detected in 7% and 23% of patients with concordant low and high risk respectively versus 14% and 20% in the discordant groups (p<0.001). Five-year disease specific survival in the discordant groups proved intermediate (75-80%) to concordant low (94%) or high (58%) risk. Both operative and preoperative biopsy high-risk results have independent prognostic impact on disease specific survival with adjusted hazard ratios of 2.4 (95% confidence interval (95% CI) 1.5-3.9) and 2.1 (95% CI 1.3-3.2) respectively by Cox analysis. CONCLUSIONS: Discordant risk in preoperative biopsy and hysterectomy identifies an intermediate group with respect to disease spread and prognosis. Preoperative biopsy results remain important also with the hysterectomy histology available.
  •  
27.
  • Yastrubchak, O., et al. (författare)
  • Ferromagnetism and the electronic band structure in (Ga,Mn)(Bi,As) epitaxial layers
  • 2014
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Impact of Bi incorporation into (Ga,Mn)As layers on their electronic-and band-structures as well as their magnetic and structural properties has been studied. Homogenous (Ga,Mn)(Bi,As) layers of high structural perfection have been grown by the low-temperature molecular-beam epitaxy technique. Post-growth annealing treatment of the layers results in an improvement of their structural and magnetic properties and an increase in the hole concentration in the layers. The modulation photoreflectance spectroscopy results are consistent with the valence-band model of hole-mediated ferromagnetism in the layers. This material combines the properties of (Ga,Mn)As and Ga(Bi,As) ternary compounds and offers the possibility of tuning its electrical and magnetic properties by controlling the alloy composition. (C) 2014 AIP Publishing LLC.
  •  
28.
  • Di Marco, Igor, et al. (författare)
  • Electron correlations in MnxGa1-xAs as seen by resonant electron spectroscopy and dynamical mean field theory
  • 2013
  • Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 4, s. 6-
  • Tidskriftsartikel (refereegranskat)abstract
    • After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.
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29.
  • Enskog, Anders, et al. (författare)
  • Uterus transplantation in the baboon: methodology and long-term function after auto-transplantation.
  • 2010
  • Ingår i: Human reproduction (Oxford, England). - : Oxford University Press (OUP). - 1460-2350 .- 0268-1161. ; 25:8, s. 1980-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Techniques for uterus transplantation (UTx) have been developed in rodent/domestic animals towards future clinical introduction of UTx to treat uterine factor infertility. The aim of this study was to extend the UTx research into a non-human primate species by developing surgical techniques for uterus retrieval and transplantation in the baboon.
  •  
30.
  • Garcia-Dios, Diego A, et al. (författare)
  • High-throughput interrogation of PIK3CA, PTEN, KRAS, FBXW7 and TP53 mutations in primary endometrial carcinoma.
  • 2013
  • Ingår i: Gynecologic Oncology. - : Elsevier BV. - 0090-8258 .- 1095-6859. ; 128:2, s. 327-334
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Endometrial cancer patients may benefit from systemic adjuvant chemotherapy, alone or in combination with targeted therapies. Prognostic and predictive markers are needed, however, to identify patients amenable for these therapies. METHODS: Primary endometrial tumors were genotyped for >100 hot spot mutations in genes potentially acting as prognostic or predictive markers. Mutations were correlated with tumor characteristics in a discovery cohort, replicated in independent cohorts and finally, confirmed in the overall population (n=1063). RESULTS: PIK3CA, PTEN and KRAS mutations were most frequently detected, respectively in 172 (16.2%), 164 (15.4%) and 161 (15.1%) tumors. Binary logistic regression revealed that PIK3CA mutations were more common in high-grade tumors (OR=2.03; P=0.001 for grade 2 and OR=1.89; P=0.012 for grade 3 compared to grade 1), whereas a positive TP53 status correlated with type II tumors (OR=11.92; P<0.001) and PTEN mutations with type I tumors (OR=19.58; P=0.003). Conversely, FBXW7 mutations correlated with positive lymph nodes (OR=3.38; P=0.045). When assessing the effects of individual hot spot mutations, the H1047R mutation in PIK3CA correlated with high tumor grade and reduced relapse-free survival (HR=2.18; P=0.028). CONCLUSIONS: Mutations in PIK3CA, TP53, PTEN and FBXW7 correlate with high tumor grade, endometrial cancer type and lymph node status, whereas PIK3CA H1047R mutations serve as prognostic markers for relapse-free survival in endometrial cancer patients.
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31.
  • Gareev, R. R., et al. (författare)
  • Giant anisotropic magnetoresistance in insulating ultrathin (Ga,Mn)As
  • 2010
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Molecular-beam epitaxy grown, 5 nm thick annealed Ga0.95Mn0.05As films demonstrate transition from metallic to insulating state for sheet resistances near resistance quantum, which we connect with the two-dimensional hole localization. Below the metal-insulator transition we found the giant anisotropic magnetoresistance (GAMR) effect, which depends on the orientation of magnetization to crystallographic axes and demonstrates the twofold symmetry angular dependence. The GAMR manifests itself in positive magnetoresistance near 50% at T=1.7 K for H//[110] crystallographic direction in contrast to smaller negative magnetoresistance for H//[110] direction. We connect the GAMR with formation of high- and low-resistance states with different localization due to anisotropic spin-orbit interaction.
  •  
32.
  • Juszynski, P., et al. (författare)
  • Influence of Epitaxial Strain on Magnetic Anisotropy in (Ga,Mn)As
  • 2012
  • Ingår i: Acta Physica Polonica. Series A: General Physics, Physics of Condensed Matter, Optics and Quantum Electronics, Atomic and Molecular Physics, Applied Physics. - 0587-4246. ; 122:6, s. 1004-1006
  • Tidskriftsartikel (refereegranskat)abstract
    • Two (Ga,Mn)As samples having different magnetic anisotropy (one with in-plane easy axis and another one with out-of-plane easy axis) were studied by means of magnetotransport experiments. Anisotropy field B-A was determined for both samples as a function of temperature. For the sample having in-plane easy axis, an inversion of the direction of planar Hall effect hysteresis was observed upon increase of temperature. This result was simulated using the Stoner-Wohlfarth model.
  •  
33.
  • Lawniczak-Jablonska, K., et al. (författare)
  • Structural and magnetic properties of GaAs:(Mn,Ga)As granular layers
  • 2011
  • Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1609-1614
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs:(Mn,Ga)As films were prepared by annealing the Ga0.92Mn0.08As/GaAs layer grown by the MBE method at low temperature. The annealing was performed at 500 or 600 degrees C. It is commonly accepted that this processing should result in formation of cubic zinc blende or hexagonal MnAs inclusions depending on the temperature. We demonstrate that such a priory assumption is not justified. The kind of formed inclusions depends not only on the annealing temperature but also on the number of defects and Mn atoms in the substitutional and interstitial positions in as grown sample. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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34.
  • Lawniczak-Jablonska, K., et al. (författare)
  • Structural and magnetic properties of nanoclusters in GaMnAs granular layers
  • 2011
  • Ingår i: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596. ; 184:6, s. 1530-1539
  • Tidskriftsartikel (refereegranskat)abstract
    • Structural and magnetic properties of GaAs thin films with embedded nanoclusters were investigated as a function of the annealing temperature and Mn content. Surprisingly, the presence of two kinds of nanoclusters with different structure was detected in most of the samples independently of the thermal processing or Mn content. This proved that the presence of a given type of clusters cannot be assumed a priori as is reported in many papers. The fraction of Mn atoms in each kind of cluster was estimated from the extended X-ray absorption fine structure analysis. This analysis ruled out the possibility of the existence of nanoclusters containing a hypothetic MnAs cubic compound-only (Ga,Mn)As cubic and hexagonal MnAs clusters were detected. Moreover the bimodal distribution of Mn magnetic moments was found, which scales with the estimated fraction of Mn atoms in the cubic and hexagonal clusters. (C) 2011 Elsevier Inc. All rights reserved.
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35.
  • Lawniczak-Jablonska, K., et al. (författare)
  • The source of room temperature ferromagnetism in granular GaMnAs layers with zinc blende clusters
  • 2011
  • Ingår i: Physica Status Solidi. Rapid Research Letters. - : Wiley. - 1862-6254. ; 5:2, s. 62-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Granular GaAs:(Mn,Ga) As films were prepared by annealing the Ga0.985Mn0.015As/GaAs layers at 500 degrees C or 600 degrees C. It is commonly accepted that this processing should result in the formation of cubic or hexagonal MnAs clusters, respectively. We demonstrate that such a priori assumption is not justified. If in the as grown sample there are not many defects with the interstitial Mn atoms, only small cubic clusters can be formed even after annealing at 600 degrees C. Moreover, in a sample containing solely cubic GaMnAs clusters, the Mn ions are ferro-magnetically coupled at room temperature. This fact was explained by the existence of GaMnAs solid solution in the clusters, with content of Mn close to 20% (higher than ever found in the layers) as was confirmed by experiment and theory. Extended X-ray absorption spectroscopy studies excluded the possibility of formation of the hypothetic zinc blende MnAs clusters. Not more than one Mn atom was detected in the second shell around central Mn atom. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  •  
36.
  • Lund, Magnus, et al. (författare)
  • Variability in exchange of CO2 across 12 northern peatland and tundra sites
  • 2010
  • Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 16:9, s. 2436-2448
  • Tidskriftsartikel (refereegranskat)abstract
    • Many wetland ecosystems such as peatlands and wet tundra hold large amounts of organic carbon (C) in their soils, and are thus important in the terrestrial C cycle. We have synthesized data on the carbon dioxide (CO2) exchange obtained from eddy covariance measurements from 12 wetland sites, covering 1-7 years at each site, across Europe and North America, ranging from ombrotrophic and minerotrophic peatlands to wet tundra ecosystems, spanning temperate to arctic climate zones. The average summertime net ecosystem exchange of CO2 (NEE) was highly variable between sites. However, all sites with complete annual datasets, seven in total, acted as annual net sinks for atmospheric CO2. To evaluate the influence of gross primary production (GPP) and ecosystem respiration (R-eco) on NEE, we first removed the artificial correlation emanating from the method of partitioning NEE into GPP and R-eco. After this correction neither R-eco (P = 0.162) nor GPP (P = 0.110) correlated significantly with NEE on an annual basis. Spatial variation in annual and summertime R-eco was associated with growing season period, air temperature, growing degree days, normalized difference vegetation index and vapour pressure deficit. GPP showed weaker correlations with environmental variables as compared with R-eco, the exception being leaf area index (LAI), which correlated with both GPP and NEE, but not with R-eco. Length of growing season period was found to be the most important variable describing the spatial variation in summertime GPP and R-eco; global warming will thus cause these components to increase. Annual GPP and NEE correlated significantly with LAI and pH, thus, in order to predict wetland C exchange, differences in ecosystem structure such as leaf area and biomass as well as nutritional status must be taken into account.
  •  
37.
  • Mercer, Elinore M, et al. (författare)
  • Multilineage Priming of Enhancer Repertoires Precedes Commitment to the B and Myeloid Cell Lineages in Hematopoietic Progenitors
  • 2011
  • Ingår i: Immunity. - : Elsevier (Cell Press). - 1074-7613 .- 1097-4180. ; 35:3, s. 413-425
  • Tidskriftsartikel (refereegranskat)abstract
    • Recent studies have documented genome-wide binding patterns of transcriptional regulators and their associated epigenetic marks in hematopoietic cell lineages. In order to determine how epigenetic marks are established and maintained during developmental progression, we have generated long-term cultures of hematopoietic progenitors by enforcing the expression of the E-protein antagonist Id2. Hematopoietic progenitors that express Id2 are multipotent and readily differentiate upon withdrawal of Id2 expression into committed B lineage cells, thus indicating a causative role for E2A (Tcf3) in promoting the B cell fate. Genome-wide analyses revealed that a substantial fraction of lymphoid and myeloid enhancers are premarked by the poised or active enhancer mark H3K4me1 in multipotent progenitors. Thus, in hematopoietic progenitors, multilineage priming of enhancer elements precedes commitment to the lymphoid or myeloid cell lineages.
  •  
38.
  • Trovik, Jone, et al. (författare)
  • Stathmin Overexpression Identifies High-Risk Patients and Lymph Node Metastasis in Endometrial Cancer.
  • 2011
  • Ingår i: Clinical cancer research : an official journal of the American Association for Cancer Research. - 1078-0432. ; 17:10, s. 3368-3377
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: Overexpression of the oncogen Stathmin has been linked to aggressive endometrial carcinoma and a potential for PI3Kinase inhibitors in this disease. We wanted to validate the prognostic value of Stathmin expression in a large prospective multicenter setting. As lymph node sampling is part of current surgical staging, we also aimed to test if Stathmin expression in endometrial curettage specimens could predict lymph node metastasis. EXPERIMENTAL DESIGN: A total of 1,076 endometrial cancer patients have been recruited from 10 centers to investigate the biological tumor marker Stathmin in relation to clinicopathologic variables, including lymph node status and survival. Stathmin immunohistochemical staining was carried out in 477 hysterectomy and 818 curettage specimens. RESULTS: Seventy-one percent of the patients (n = 763) were subjected to lymph node sampling, of which 12% had metastatic nodes (n = 94). Overexpression of Stathmin was detected in 37% (302 of 818) of the curettage and in 18% (84 of 477) of the hysterectomy specimens investigated. Stathmin overexpression in curettage and hysterectomy specimens were highly correlated and significantly associated with nonendometrioid histology, high grade, and aneuploidy. Stathmin analysis in preoperative curettage samples significantly correlated with, and was an independent predictor of, lymph node metastases. High Stathmin expression was associated with poor disease-specific survival (P ≤ 0.002) both in curettage and hysterectomy specimens. CONCLUSIONS: Stathmin immunohistochemical staining identifies endometrial carcinomas with lymph node metastases and poor survival. The value, as a predictive marker for response to PI3Kinase inhibition and as a tool to stratify patients for lymph node sampling in endometrial carcinomas, remains to be determined. Clin Cancer Res; 17(10); 3368-77. ©2011 AACR.
  •  
39.
  • Werner, H M J, et al. (författare)
  • Revision of FIGO surgical staging in 2009 for endometrial cancer validates to improve risk stratification.
  • 2012
  • Ingår i: Gynecologic oncology. - : Elsevier BV. - 1095-6859 .- 0090-8258. ; 125:1, s. 103-108
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Correct staging is a cornerstone in cancer treatment. The FIGO surgical staging for endometrial cancer was revised in 2009. We have evaluated if the revision improved stratification with respect to prognosis in a large prospective multicenter setting. METHODS: 1268 endometrial cancer patients have been prospectively recruited in the MoMaTEC study for the investigation of clinical and histopathological data. RESULTS: Restaging from FIGO 88 to FIGO 09 criteria increased the number of stage I cases from 932 to 979. The majority of the non-endometrioid tumors, down-staged to FIGO 09 stage I, were of serous histology. One third of the patients classified as stage II tumors based on FIGO 88 criteria (FIGO88 IIA) were down-staged to FIGO 09 IA (53%) and FIGO 09 IB (47%). The histological subtype for these cases was mainly endometrioid (86.1%) and high/intermediate grade (77.7%). Patients with FIGO 88 stages IA, IB, IIA and IIIA with positive cytology only, showed similar survival. In Cox multivariate survival analysis adjusting for histopathological variables we found that the revised FIGO 09 criteria improved prognostication. For FIGO stage I patients the adjusted HR was 3.9 (p=0.01, CI 1.35-11.36) for FIGO IB compared to FIGO IA. The independent prognostic impact for the FIGO 09 staging was also confirmed in a subset analysis of patients not subjected to lymphadenectomy and for the endometrioid subgroup. CONCLUSIONS: The FIGO 2009 staging system has improved prediction of prognosis, and is less complex, compared to earlier versions. Careful assessment of myometrial invasion seems particularly important for patients not subjected to lymphadenectomy.
  •  
40.
  • Wolska, A., et al. (författare)
  • MnSb inclusions in the GaSb matrix studied by X-ray absorption spectroscopy
  • 2011
  • Ingår i: Radiation Physics and Chemistry. - : Elsevier BV. - 0969-806X. ; 80:10, s. 1026-1030
  • Konferensbidrag (refereegranskat)abstract
    • The MBE processes were performed in order to form the MnSb inclusions. Two kinds of substrates (GaSb and GaAs) as well as growth temperatures (450 and 520 degrees C) were examined. SEM imaging was performed to determine the shape and size of formed inclusions. In all the samples the inclusions of few hundred nm were formed. Their shapes depended strongly on the type of substrate while the size slightly increases with the growth temperature. The X-ray absorption techniques were used to monitor the local structure around Mn atoms and confirmed that the neighborhood of Mn atoms in the layers was close to that of the MnSb reference powder. We succeed in the formation of the GaSb layers with Mn assembled only into MnSb inclusions on both types of substrates: GaAs(1 1 1)A and GaSb(1 00). However, in case of the GaAs(1 1 1)A substrates, the atomic order around Mn atoms in MnSb inclusions is less perfect than in case of the GaSb(1 0 0) substrates. (C) 2011 Elsevier Ltd. All rights reserved.
  •  
41.
  • Yastrubchak, O., et al. (författare)
  • Ion-Implantation Control of Ferromagnetism in (Ga,Mn)As Epitaxial Layers
  • 2010
  • Ingår i: Journal Of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 39:6, s. 794-798
  • Konferensbidrag (refereegranskat)abstract
    • Epitaxial layers of (Ga,Mn)As ferromagnetic semiconductor have been subjected to low-energy ion implantation by applying a very low fluence of either chemically active, oxygen ions or inactive ions of neon noble gas. Several complementary characterization techniques have been used with the aim of studying the effect of ion implantation on the layer properties. Investigation of their electrical and magnetic properties revealed that implantation with either O or Ne ions completely suppressed both the conductivity and ferromagnetism in the layers. On the other hand, Raman spectroscopy measurements evidenced that O ion implantation influenced optical properties of the layers noticeably stronger than did Ne ion implantation. Moreover, structural modifications of the layers caused by ion implantation were investigated using high-resolution x-ray diffraction technique. A mechanism responsible for ion-implantation-induced suppression of the conductivity and ferromagnetism in (Ga,Mn)As layers, which could be applied as a method for tailoring nanostructures in the layers, is discussed in terms of defects created in the layers by the two implanted elements.
  •  
42.
  • Zipper, Elzbieta, et al. (författare)
  • Spin relaxation in semiconductor quantum rings and dots-a comparative study
  • 2011
  • Ingår i: Journal of Physics: Condensed Matter. - : IOP Publishing. - 1361-648X .- 0953-8984. ; 23:11
  • Tidskriftsartikel (refereegranskat)abstract
    • We calculate spin relaxation times due to spin-orbit-mediated electron-phonon interactions for experimentally accessible semiconductor quantum ring and dot architectures. We elucidate the differences between the two systems due to different confinement. The estimated relaxation times (at B = 1 T) are in the range between a few milliseconds to a few seconds. This high stability of spin in a quantum ring allows us to test it as a spin qubit. A brief discussion of quantum state manipulations with such a qubit is presented.
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