| 1. |
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| 2. |
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| 3. |
- Abate, E., et al.
(author)
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Combined performance tests before installation of the ATLAS Semiconductor and Transition Radiation Tracking Detectors
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3
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Journal article (peer-reviewed)abstract
- The ATLAS (A Toroidal LHC ApparatuS) Inner Detector provides charged particle tracking in the centre of the ATLAS experiment at the Large Hadron Collider (LHC). The Inner Detector consists of three subdetectors: the Pixel Detector, the Semiconductor Tracker (SCT), and the Transition Radiation Tracker (TRT). This paper summarizes the tests that were carried out at the final stage of SCT+TRT integration prior to their installation in ATLAS. The combined operation and performance of the SCT and TRT barrel and endcap detectors was investigated through a series of noise tests, and by recording the tracks of cosmic rays. This was a crucial test of hardware and software of the combined tracker detector systems. The results of noise and cross-talk tests on the SCT and TRT in their final assembled configuration, using final readout and supply hardware and software, are reported. The reconstruction and analysis of the recorded cosmic tracks allowed testing of the offline analysis chain and verification of basic tracker performance parameters, such as efficiency and spatial resolution, in combined operation before installation.
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| 4. |
- Abat, E., et al.
(author)
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Study of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV
- 2009
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002 .- 1872-9576. ; 607:2, s. 372-386
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Journal article (peer-reviewed)abstract
- A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. in this paper, the response of the central calorimeters to pions with energies in the range between 3 and 9 GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4. (C) 2009 Elsevier B.V. All rights reserved.
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| 5. |
- Abat, E., et al.
(author)
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The ATLAS TRT end-cap detectors
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3
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Journal article (peer-reviewed)abstract
- The ATLAS TRT end-cap is a tracking drift chamber using 245,760 individual tubular drift tubes. It is a part of the TRT tracker which consist of the barrel and two end-caps. The TRT end-caps cover the forward and backward pseudo-rapidity region 1.0 < vertical bar eta vertical bar < 2.0, while the TRT barrel central eta region vertical bar eta vertical bar < 1.0. The TRT system provides a combination of continuous tracking with many measurements in individual drift tubes ( or straws) and of electron identification based on transition radiation from fibers or foils interleaved between the straws themselves. Along with other two sub-systems, namely the Pixel detector and Semi Conductor Tracker (SCT), the TRT constitutes the ATLAS Inner Detector. This paper describes the recently completed and installed TRT end-cap detectors, their design, assembly, integration and the acceptance tests applied during the construction.
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| 6. |
- Adcox, K, et al.
(author)
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Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration
- 2005
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In: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 757:1-2, s. 184-283
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Research review (peer-reviewed)abstract
- Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (PT), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high PT. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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| 7. |
- Abat, E., et al.
(author)
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The ATLAS Transition Radiation Tracker (TRT) proportional drift tube: design and performance
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3:2
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Journal article (peer-reviewed)abstract
- A straw proportional counter is the basic element of the ATLAS Transition Radiation Tracker (TRT). Its detailed properties as well as the main properties of a few TRT operating gas mixtures are described. Particular attention is paid to straw tube performance in high radiation conditions and to its operational stability.
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| 8. |
- Abat, E., et al.
(author)
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The ATLAS TRT barrel detector
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3
-
Journal article (peer-reviewed)abstract
- The ATLAS TRT barrel is a tracking drift chamber using 52,544 individual tubular drift tubes. It is one part of the ATLAS Inner Detector, which consists of three sub-systems: the pixel detector spanning the radius range 4 to 20 cm, the semiconductor tracker (SCT) from 30 to 52 cm, and the transition radiation tracker ( TRT) from 56 to 108 cm. The TRT barrel covers the central pseudo-rapidity region |eta| < 1, while the TRT endcaps cover the forward and backward eta regions. These TRT systems provide a combination of continuous tracking with many measurements in individual drift tubes ( or straws) and of electron identification based on transition radiation from fibers or foils interleaved between the straws themselves. This paper describes the recently-completed construction of the TRT Barrel detector, including the quality control procedures used in the fabrication of the detector.
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| 9. |
- Abat, E., et al.
(author)
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The ATLAS TRT electronics
- 2008
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In: Journal of Instrumentation. - 1748-0221. ; 3:6
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Journal article (peer-reviewed)abstract
- The ATLAS inner detector consists of three sub-systems: the pixel detector spanning the radius range 4cm-20cm, the semiconductor tracker at radii from 30 to 52 cm, and the transition radiation tracker (TRT), tracking from 56 to 107 cm. The TRT provides a combination of continuous tracking with many projective measurements based on individual drift tubes (or straws) and of electron identification based on transition radiation from fibres or foils interleaved between the straws themselves. This paper describes the on and off detector electronics for the TRT as well as the TRT portion of the data acquisition (DAQ) system.
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| 10. |
- Elsik, Christine G., et al.
(author)
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The Genome Sequence of Taurine Cattle : A Window to Ruminant Biology and Evolution
- 2009
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 324:5926, s. 522-528
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Journal article (peer-reviewed)abstract
- To understand the biology and evolution of ruminants, the cattle genome was sequenced to about sevenfold coverage. The cattle genome contains a minimum of 22,000 genes, with a core set of 14,345 orthologs shared among seven mammalian species of which 1217 are absent or undetected in noneutherian (marsupial or monotreme) genomes. Cattle-specific evolutionary breakpoint regions in chromosomes have a higher density of segmental duplications, enrichment of repetitive elements, and species-specific variations in genes associated with lactation and immune responsiveness. Genes involved in metabolism are generally highly conserved, although five metabolic genes are deleted or extensively diverged from their human orthologs. The cattle genome sequence thus provides a resource for understanding mammalian evolution and accelerating livestock genetic improvement for milk and meat production.
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| 11. |
- Tuskan, G A, et al.
(author)
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The genome of black cottonwood, Populus trichocarpa (Torr. & Gray).
- 2006
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 313:5793, s. 1596-604
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Journal article (peer-reviewed)abstract
- We report the draft genome of the black cottonwood tree, Populus trichocarpa. Integration of shotgun sequence assembly with genetic mapping enabled chromosome-scale reconstruction of the genome. More than 45,000 putative protein-coding genes were identified. Analysis of the assembled genome revealed a whole-genome duplication event; about 8000 pairs of duplicated genes from that event survived in the Populus genome. A second, older duplication event is indistinguishably coincident with the divergence of the Populus and Arabidopsis lineages. Nucleotide substitution, tandem gene duplication, and gross chromosomal rearrangement appear to proceed substantially more slowly in Populus than in Arabidopsis. Populus has more protein-coding genes than Arabidopsis, ranging on average from 1.4 to 1.6 putative Populus homologs for each Arabidopsis gene. However, the relative frequency of protein domains in the two genomes is similar. Overrepresented exceptions in Populus include genes associated with lignocellulosic wall biosynthesis, meristem development, disease resistance, and metabolite transport.
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| 12. |
- Cwetanski, P, et al.
(author)
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Acceptance tests and criteria of the ATLAS transition radiation tracker
- 2005
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In: IEEE Transactions on Nuclear Science. - 0018-9499. ; 52:6, s. 2911-2916
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Journal article (peer-reviewed)abstract
- The Transition Radiation Tracker (TRT) sits at the outermost part of the ATLAS Inner Detector, encasing the Pixel Detector and the Semi-Conductor Tracker (SCT). The TRT combines charged particle track reconstruction with electron identification capability. This is achieved by layers of xenonfilled straw tubes with periodic radiator foils or fibers providing TR photon emission. The design and choice of materials have been optimized to cope with the harsh operating conditions at the LHC, which are expected to lead to an accumulated radiation dose of 10 Mrad and a neutron fluence of up to 2 . 10(14) n/cm(2) after ten years of operation. The TRT comprises a barrel containing 52 000 axial straws and two end-cap parts with 320 000 radial straws. The total of 420 000 electronic channels (two channels per barrel straw) allows continuous tracking with many projective measurements (more than 30 straw hits per track). The assembly of the barrel modules in the US has recently been completed, while the end-cap wheel construction in Russia has reached the 50% mark. After testing at the production sites and shipment to CERN, all modules and wheels undergo a series of quality and conformity measurements. These acceptance tests survey dimensions, wire tension, gas-tightness, high-voltage stability and gas-gain uniformity along each individual straw. This paper gives details on the acceptance criteria and measurement methods. An overview of the most important results obtained to-date is also given.
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| 13. |
- Sodergren, Erica, et al.
(author)
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The genome of the sea urchin Strongylocentrotus purpuratus.
- 2006
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In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 314:5801, s. 941-52
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Journal article (peer-reviewed)abstract
- We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes.
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| 14. |
- De Luca, L., et al.
(author)
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Early pharmacological treatment of acute heart failure syndromes: A systematic review of clinical trials
- 2007
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In: Acute cardiac care. - 1748-2941. ; 9:1, s. 10-21
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Journal article (peer-reviewed)abstract
- Context: Acute Heart Failure Syndromes (AHFS) is a common admission diagnosis associated with high mortality and hospital readmissions. Given the mixed results of recent clinical trials, the early management of AHFS remains controversial. Objective: To review the recent evidence regarding current and investigational therapies for the early management of AHFS. Data Sources: A systematic search of peer-reviewed publications was performed on MEDLINE and EMBASE from January 1990 to August 2006. The results of unpublished or ongoing trials were obtained from presentations at national and international meetings and pharmaceutical industry releases. Bibliographies from these references were also reviewed, as were additional articles identified by content experts. Study Selection and Data Extraction: Criteria used for study selection were controlled study design, relevance to clinicians and validity based on venue of publication and power analysis. Data Synthesis: Although all current intravenous therapies for the early management of AHFS appear to improve hemodynamics, this may not always translate into short-term clinical benefit. Conclusion: The results of the trials conducted to date in AHFS have generally been disappointing. There is, therefore, an unmet need for new therapeutic approaches for the early management of AHFS that may improve the short-term and long-term outcomes.
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| 15. |
- Chung, S. J., et al.
(author)
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Magneto-transport properties of a GaMnAs-based ferromagnetic semiconductor trilayer structure grown on a ZnMnSe buffer
- 2008
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In: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 37:6, s. 912-916
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Journal article (peer-reviewed)abstract
- Magneto-transport properties have been investigated in a ferromagnetic GaMnAs/GaAlAs/GaMnAs semiconductor trilayer structure grown on a ZnMnSe buffer layer. The presence of the ZnMnSe buffer leads to the formation of a spin-valve-like structure, which provides the opportunity to investigate spin scattering effects by Hall resistance and magnetoresistance (MR) measurements in the current-in-plane (CIP) configuration. The Curie temperature (T c) and coercivity of the bottom GaMnAs layer are observed to be different from those of the top GaMnAs layer due to the proximity effect between the ferromagnetic GaMnAs and paramagnetic ZnMnSe layers. A two-step behavior is observed in the hysteresis loops of the Hall resistance, indicating that the coercive fields are different in the two GaMnAs layers in the trilayer structure. The magnetoresistance (MR) measured simultaneously with the Hall resistance shows a sudden increase in the field region where the magnetization of the two GaMnAs layers is different. Although the MR ratio was observed to be only 0.04% in our trilayer structure (due to the experimental CIP configuration), the study clearly demonstrates the presence of spin scattering in a trilayer ferromagnetic semiconductor structure grown on a ZnMnSe buffer. © 2008 TMS.
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| 16. |
- Chung, S. J., et al.
(author)
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Time stability of multi-domain states formed in the magnetization reversal process of GaMnAs film
- 2007
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In: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 143:4-5, s. 232-235
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Journal article (peer-reviewed)abstract
- The magnetization reversal process of ferromagnetic GaMnAs epilayers has been systematically investigated using the planar Hall effect (PHE) and magnetoresistance (MR). We have observed non-abrupt transitions between two orientations of magnetization in PHE and striking resistance dips at the second switching in MR. The observed behaviors indicate that multi-domain structures are formed as magnetization undergoes a reorientation. An asymmetric PHE hysteresis loop was obtained when the range of the field scan was restricted to fields below the final magnetization transition. This indicates that the domain structure formed at the moment of magnetization reorientation remains stable even after the magnetic field is removed. The time stability of the multi-domain structure was further tested by monitoring the change in the planar Hall resistance value for more than 24 h.
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| 17. |
- Durand, Caylib A, et al.
(author)
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Phosphoinositide 3-kinase p110 delta regulates natural antibody production, marginal zone and B-1 B cell function, and autoantibody responses.
- 2009
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In: Journal of immunology (Baltimore, Md. : 1950). - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 183:9, s. 5673-84
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Journal article (peer-reviewed)abstract
- B-1 and marginal zone (MZ) B cells produce natural Abs, make Ab responses to microbial pathogens, and contribute to autoimmunity. Although the delta isoform of the PI3K p110 catalytic subunit is essential for development of these innate-like B cells, its role in the localization, activation, and function of normal B-1 and MZ B cells is not known. Using IC87114, a highly selective inhibitor of p110delta enzymatic activity, we show that p110delta is important for murine B-1 and MZ B cells to respond to BCR clustering, the TLR ligands LPS and CpG DNA, and the chemoattractants CXCL13 and sphingosine 1-phosphate. In these innate-like B cells, p110delta activity mediates BCR-, TLR- and chemoattractant-induced activation of the Akt prosurvival kinase, chemoattractant-induced migration, and TLR-induced proliferation. Moreover, we found that TLR-stimulated Ab responses by B-1 and MZ B cells, as well as the localization of MZ B cells in the spleen, depend on p110delta activity. Finally, we show that the in vivo production of natural Abs requires p110delta and that p110delta inhibitors can reduce in vivo autoantibody responses. Thus, targeting p110delta may be a novel approach for regulating innate-like B cells and for treating Ab-mediated autoimmune diseases.
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| 18. |
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| 19. |
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| 20. |
- Huang, C, et al.
(author)
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The inhomogeneous structure of water at ambient conditions
- 2009
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In: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 106:36, s. 15214-15218
-
Journal article (peer-reviewed)abstract
- Small-angle X-ray scattering (SAXS) is used to demonstrate the presence of density fluctuations in ambient water on a physical length-scale of approximate to 1 nm; this is retained with decreasing temperature while the magnitude is enhanced. In contrast, the magnitude of fluctuations in a normal liquid, such as CCl4, exhibits no enhancement with decreasing temperature, as is also the case for water from molecular dynamics simulations under ambient conditions. Based on X-ray emission spectroscopy and X-ray Raman scattering data we propose that the density difference contrast in SAXS is due to fluctuations between tetrahedral-like and hydrogen-bond distorted structures related to, respectively, low and high density water. We combine our experimental observations to propose a model of water as a temperature-dependent, fluctuating equilibrium between the two types of local structures driven by incommensurate requirements for minimizing enthalpy (strong near-tetrahedral hydrogen-bonds) and maximizing entropy (non-directional H-bonds and disorder). The present results provide experimental evidence that the extreme differences anticipated in the hydrogen-bonding environment in the deeply supercooled regime surprisingly remain in bulk water even at conditions ranging from ambient up to close to the boiling point.
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| 21. |
- Kim, T., et al.
(author)
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Strain-engineered magnetic anisotropy of GaMnAs ferromagnetic semiconductors
- 2007
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In: Journal of the Korean Physical Society. - : Korean Physical Society. - 0374-4884 .- 1976-8524. ; 50:3, s. 829-833
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Journal article (peer-reviewed)abstract
- A series of GaMnAs epilayers grown on GaInAs buffer layers have been investigated. The concentrations of Mn in the GaMnAs layer and In in the GaInAs layer were varied in the series, for which the tensile strain condition for the GaMnAs layer are systematically changed. The X-ray measurement provided the lattice constants of the layers, from which the stain of the GaMnAs layer was determined. The magneto-transport data revealed in-plane anisotropy in the GaMnAs sample grown on a GaInAs buffer with a low concentration of In. Such in-plan magnetic anisotropy of the GaMnAs layer continuously changed to a vertical magnetic anisotropy when the tensile strain was increased in the sample grown on the GaInAs buffer with a higher In concentration. This experiment clearly demonstrated that the magnetic anisotropy of GaMnAs could be continuously engineered by using the strain introduced by the GaInAs buffer layers.
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| 22. |
- Lee, S., et al.
(author)
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Tunable quaternary states in ferromagnetic semiconductor GaMnAs single layer for memory devices
- 2007
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 90:15
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Journal article (peer-reviewed)abstract
- The authors show that staggered asymmetric planar Hall resistance (PHR) loops observed in GaMnAs ferromagnetic semiconductor films with biaxial in-plane magnetic anisotropy result in four stable resistance states at zero magnetic field owing to the formation of a stable multidomain structure during magnetization reversal. The values of PHR can be systematically controlled by changing the direction and the scanning range of the applied magnetic field. The possibility of a quaternary memory device based on the observed four PHR states is demonstrated by obtaining consistent results in the writing process using appropriate sequences of magnetic field pulses. © 2007 American Institute of Physics.
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| 23. |
- Petri, Michelle, et al.
(author)
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Systemic lupus international collaborating clinics renal activity/response exercise - Development of a renal activity score and renal response index
- 2008
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In: Arthritis and Rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 58:6, s. 1784-1788
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Journal article (peer-reviewed)abstract
- Objective. To develop a measure of renal activity in systemic lupus erythematosus and use it to develop a renal response index. Methods. Abstracted data from the medical records of 215 patients with lupus nephritis were sent to 8 nephrologists and 29 rheumatologists for rating. Seven nephrologists and 22 rheumatologists completed the ratings. Each physician rated each patient visit with respect to renal disease activity (none, mild, moderate, or severe). Using the most commonly selected rating for each patient as the gold standard, stepwise regression modeling was performed to identify the variables most related to renal disease activity, and these variables were then used to create an activity score. This activity score could then be applied to 2 consecutive visits to define a renal response index. Results. The renal activity score was computed as follows: proteinuria 0.5-1 gm/day (3 points), proteinuria >1-3 gm/day (5 points), proteinuria >3 gm/day (11 points), urine red blood cell count > 10/high-power field (3 points), and urine white blood cell count >10/high-power field (I point). The chance-adjusted agreement between the renal response index derived from the activity score applied to the paired visits and the plurality physician response rating was 0.69 (95% confidence interval 0.59-0.79). Conclusion. Ratings derived from this index for rating of renal response showed reasonable agreement with physician ratings in a pilot study. The index will require further refinement, testing, and validation. A data-driven approach to create renal activity and renal response indices will be useful in both clinical care and research settings.
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| 24. |
- Robinson, Nathaniel D., et al.
(author)
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Doping front propagation in light-emitting electrochemical cells
- 2006
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:155210
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Journal article (peer-reviewed)abstract
- Observations of the expansion of the p- and n-doped regions in planar (lateral) polymer light-emitting electrochemical cells with large (mm-sized) interelectrode gaps driven with 5 to 50 V have inspired a model describing the doping front propagation. We find that the propagation is limited by the movement of ions in the electronically insulating region between the p- and n-doped regions. Two consequences of an ion-limited front propagation are that the doping fronts accelerate as they approach each other, and that fingerlike protrusions are formed, particularly at larger drive voltages.
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| 25. |
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| 26. |
- Shin, D. W., et al.
(author)
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Size dependence of the electronic structure of copper nanoclusters in SiC matrix
- 2006
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In: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 422:4-6, s. 543-546
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Journal article (peer-reviewed)abstract
- We studied the size dependence of the electronic structure of nanocrystalline copper embedded in silicon carbide by means of soft Xray absorption spectroscopy. Changes in the local electronic states of copper nanoclusters, including the shift in binding energy and the reduction of s-p-d hybridization, occurred. The experimental result was compared with the ab initio self-consistent, real-space, multiple-scattering calculation. The calculation was in good agreement with the trend found in our experimental results. We concluded that the reduction of d-d interaction and the concomitant changes in s-p-d hybridization in copper nanoclusters arise due to the surface effect.
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| 27. |
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| 28. |
- Shin, D. Y., et al.
(author)
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Precise investigation of domain pinning energy in GaMnAs using planar hall effect and magnetoresistance measurements
- 2007
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In: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 43:6, s. 3025-3027
-
Journal article (peer-reviewed)abstract
- The planar Hall effect (PHE) and magnetoresistance (MR) measurements have been carried out on a GaMnAs ferromagnetic semiconductor. The PHE and MR spectra exhibit interesting two-step magnetization switching behavior arising from the magnetic anisotropy properties of the system. By fitting the angle-dependent planar Hall resistance (PHR) data taken at 5 kG with the Stoner-Wohlfarth model, the cubic and uniaxial anisotropy constants were independently obtained. The anisotropy constants lead to the precise determination of easy axis direction, which turns out to be in good agreement with the easy axis determined from the angular plot of the switching field. The domain pinning energies were further obtained by fitting the angle dependence of the switching field, including the effect of uniaxial anisotropy. © 2007 IEEE.
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| 29. |
- Shin, D. Y., et al.
(author)
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Stable multidomain structures formed in the process of magnetization reversal in GaMnAs ferromagnetic semiconductor thin films
- 2007
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 98:4
-
Journal article (peer-reviewed)abstract
- The process of magnetization reversal in ferromagnetic Ga(1-x)MnxAs epilayers has been systematically investigated using the planar Hall effect (PHE). Interestingly, we have observed a pronounced asymmetry in the PHE hysteresis when the range of the field scan is restricted to fields below the final magnetization transition. The observed behavior indicates that (a)A multidomain structures are formed as M undergoes a reorientation, (b) the domain landscape formed in this way remains stable even after the magnetic field is switched off, and (c) the reorientation of magnetization directions corresponding to the transition points in PHE takes place separately within each domain. © 2007 The American Physical Society.
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| 30. |
- Shin, D. Y., et al.
(author)
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Temperature dependence of magnetic anisotropy in ferromagnetic (Ga,Mn)As films : Investigation by the planar Hall effect
- 2007
-
In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:3
-
Journal article (peer-reviewed)abstract
- We carried out systematic planar Hall effect (PHE) measurements of GaMnAs ferromagnetic semiconductor film as a function of temperature. The two-step switching of the PHE occurring in the magnetization-reversal process was observed to change significantly as the temperature was increased. To investigate the mechanism responsible for such behavior, the temperature dependence of the PHE was continuously measured (with and without an external magnetic field) after the sample was first magnetized along one of the easy axes to produce an initial single-domain state at 3 K. A detailed temperature dependence of the magnetization direction was then obtained by taking the ratio of the planar Hall resistance measured with and without a magnetic field. As the temperature was increased, the direction of the easy axis of magnetization was observed to change from the [010] crystallographic direction to [110]. This reorientation of the easy axis direction can be understood in terms of the temperature dependence of the relative strengths of the magnetic anisotropy constants (i.e., of the ratio of uniaxial-to-cubic anisotropy) of the GaMnAs film. © 2007 The American Physical Society.
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| 31. |
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| 32. |
- Shin, Joon Ho, et al.
(author)
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Polymer Light-Emitting Electrochemical Cells: Doping Concentration, Emission Zone Position, and Turn-on Time.
- 2007
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In: Advanced Functional Materials. ; 17, s. 1807-1813
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Journal article (peer-reviewed)abstract
- By direct optical probing of the doping progression and simultaneous recording of the current-time behavior, we are able to establish the position of the light-emitting p-n junction, the doping concentrations in the p- and n-type regions, and the turn-on time for a number of planar light-emitting electrochemical cells (LECs) with a 1 mm interelectrode gap. We find that the position of the p-n junction in such LECs with Au electrodes contacting an active material mixture of poly(2-methoxy,5-(2’-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV), poly(ethylene oxide), and a XCF3SO3 salt (X = Li, K, Rb) is dependent on the salt selection: for X = Li the p-n junction is positioned very close to the negative electrode, while for X = K, Rb it is significantly more centered in the interelectrode gap. We demonstrate that this results from that the p-type doping concentration is independent on salt selection at ~21020 cm-3 (~0.1 dopants/MEH-PPV repeat unit), while the n-type doping concentration exhibits a strong dependence: for X = K it is ~51020 cm-3 (~0.2 dopants/repeat unit), for X = Rb it is ~91020 cm-3 (~0.4 dopants/repeat unit), and for X = Li it is ~31021 /cm-3 (~1 dopants/repeat unit). Finally, we demonstrate that X = K, Rb devices exhibit significantly faster turn-on times than X = Li devices, which is a consequence of a higher ionic conductivity in the former devices.
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| 33. |
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| 34. |
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| 35. |
- Yea, S.-y., et al.
(author)
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Effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs films studied by planar Hall effect
- 2008
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In: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 147:7-8, s. 309-312
-
Journal article (peer-reviewed)abstract
- We have investigated the effect of chemical etching on magnetic anisotropy of ferromagnetic GaMnAs film using the planar Hall effect (PHE). Different thicknesses were obtained on a single GaMnAs specimen by using different etching times on selected areas, and the PHE was then measured using the Hall bar configurations patterned on the area. Cubic and uniaxial anisotropy fields were obtained for the films by fitting the angular dependence of the PHE data to the Stoner-Wohlfarth model. The results exhibited a very systematic dependence on the etched thickness, demonstrating that the chemical etching process significantly affects the magnetic anisotropy of ferromagnetic GaMnAs films.
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