| 1. |
- Abazov, V. M., et al.
(author)
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The upgraded DO detector
- 2006
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
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Journal article (peer-reviewed)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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| 2. |
- Abdel-Hafiez, Mahmoud, et al.
(author)
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Pressure-induced reentrant transition in NbS3 phases : Combined Raman scattering and x-ray diffraction study
- 2019
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In: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 99:23
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Journal article (peer-reviewed)abstract
- We report the evolution of charge density wave states under pressure for two NbS3 phases: triclinic (phase I) and monoclinic (phase II) at room temperature. Raman and x-ray diffraction (XRD) techniques are applied. The x-ray studies on the monoclinic phase under pressure show a compression of the lattice at different rates below and above similar to 7 GPa but without a change in space group symmetry. The Raman spectra of the two phases evolve similarly with pressure; all peaks almost disappear in the similar to 6-8 GPa range, indicating a transition from an insulating to a metallic state, and peaks at new positions appear above 8 GPa. The results suggest suppression of the ambient charge-density waves and their subsequent recovery with new orderings above 8 GPa.
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| 3. |
- Pogorily, A. N., et al.
(author)
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Magnetic anisotropy of epitaxial Co2Fe-Ge Heusler alloy films on MgO (100) substrates
- 2017
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In: AIP Advances. - : American Institute of Physics Inc.. - 2158-3226. ; 7:5
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Journal article (peer-reviewed)abstract
- Films of Co2Fe-Ge Heusler alloy with variable Ge concentration deposited on monocrystalline MgO (100) substrates by magnetron co-sputtering are investigated using microstructural, morphological, magnetometric, and magnetic resonance methods. The films were found to grow epitaxially, with island-like or continuous-layer morphology depending the Ge-content. The ferromagnetic resonance data versus out-of-plane and in-plane angle indicate the presence of easy plane and 4-fold in-plane anisotropy. The magnetometry data indicate additional weak 2-fold in-plane anisotropy and pronounced at low fields rotatable anisotropy. The observed magnetic anisotropy properties discussed in correlation with the microstructure and morphology of the films.
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| 4. |
- Payne, T. E., et al.
(author)
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Guidelines for thermodynamic sorption modelling in the context of radioactive waste disposal
- 2013
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In: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152. ; 42, s. 143-156
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Journal article (peer-reviewed)abstract
- Thermodynamic sorption models (TSMs) offer the potential to improve the incorporation of sorption in environmental modelling of contaminant migration. One specific application is safety cases for radioactive waste repositories, in which radionuclide sorption on mineral surfaces is usually described using distribution coefficients (K-d values). TSMs can be utilised to provide a scientific basis for the range of K-d values included in the repository safety case, and for assessing the response of K-d to changes in chemical conditions. The development of a TSM involves a series of decisions on model features such as numbers and types of surface sites, sorption reactions and electrostatic correction factors. There has been a lack of consensus on the best ways to develop such models, and on the methods of determination of associated parameter values. The present paper therefore presents recommendations on a number of aspects of model development, which are applicable both to radioactive waste disposal and broader environmental applications.The TSM should be calibrated using a comprehensive sorption data set for the contaminant of interest, showing the impact of major geochemical parameters including pH, ionic strength, contaminant concentration, the effect of ligands, and major competing ions. Complex natural materials should be thoroughly characterised in terms of mineralogy, surface area, cation exchange capacity, and presence of impurities. During the application of numerical optimisation programs to simulate sorption data, it is often preferable that the TSM should be fitted to the experimentally determined K-d parameter, rather than to the frequently used percentage sorbed. Two different modelling approaches, the component additivity and generalised composite, can be used for modelling sorption data for complex materials such as soils. Both approaches may be coupled to the same critically reviewed aqueous thermodynamic data sets, and may incorporate the same, or similar, surface reactions and surface species. The quality of the final sorption model can be assessed against the following characteristics: an appropriate level of complexity, documented and traceable decisions, internal consistency, limitations on the number of adjustable parameter values, an adequate fit to a comprehensive calibration data set, and capability of simulating independent data sets. Key recommendations for the process of TSM development include: definition of modelling objectives, identification of major decision points, a clear decision-making rationale with reference to experimental or theoretical evidence, utilisation of a suitable consultative and iterative model development process, testing to the maximum practicable extent, and thorough documentation of key decisions. These recommendations are consistent with international benchmarks for environmental modelling.
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| 5. |
- Spasov, S., et al.
(author)
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Terahertz imaging with a highly-sensitive quantum dot detector
- 2010
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In: 21st International Symposium on Space Terahertz Technology 2010, ISSTT 2010; Oxford; United Kingdom; 23 March 2010 through 25 March 2010. - 9781617823626 ; , s. 266-
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Conference paper (peer-reviewed)abstract
- We report on an application of photon counting detector in the sub-terahertz range of electromagnetic waves for imaging of natural and stimulated radiation emitted by free standing objects. The detector is assembled from a GaAs/AlGaAs quantum dot, electron reservoir and quantum point contact (QPC). Its operation relies on photon-to-plasmon and plasmon-to-charge conversion, followed by charge measurement in a single-shot mode. Individual photons excite plasma waves in the quantum dot, with a resonance frequency determined by the shape of the QD confining potential. The plasma wave decays subsequently by single-particle electron-hole excitations, which change the electrostatic potential stepwise in the close proximity to the QD. The potential steps are probed with the QPC operating as a sensitive electrometer. A studied object is placed on a twodimensional translating stage. Its emission is projected through an optical window onto the detector attached to a 1K cold finger in a cryostat. Subsequently translating the stage in two space directions we are able to map the distribution of the emitted radiation. The presented technique has a potential for imaging of objects passively radiated in the sub-terahertz range.
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| 6. |
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| 7. |
- Kulik, L V, et al.
(author)
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Electron spin-lattice relaxation of the so state of the oxygen-evolving complex in photosystem II and of dinuclear manganese model complexes
- 2005
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In: Biochemistry. - : AMER CHEMICAL SOC. - 0006-2960 .- 1520-4995. ; 44:26, s. 9368-9374
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Journal article (peer-reviewed)abstract
- The temperature dependence of the electron spin-lattice relaxation time T, was measured for the So state of the oxygen-evolving complex (OEC) in photosystem II and for two dinuclear manganese model complexes by pulse EPR using the inversion-recovery method. For [Mn(III)Mn(IV)(mu-O)(2)bipy(4)]ClO4, the Raman relaxation process dominates at temperatures below 50 K. In contrast, Orbach type relaxation was found for [Mn(II)Mn(III)(mu-OH)(mu-piv)(2)(Me(3)tacn)(2)](ClO4)(2) between 4.3 and 9 K. For the latter complex, an energy separation of 24.7-28.0 cm(-1) between the ground and the first excited electronic state was determined. In the So state of photosystem II, the T-1 relaxation times were measured in the range of 4.3-6.5 K. A comparison with the relaxation data (rate and pre-exponential factor) of the two model complexes and of the S-2 state of photosystem II indicates that the Orbach relaxation process is dominant for the So state and that its first excited state lies 21.7 +/- 0.4 cm(-1) above its ground state. The results are discussed with respect to the structure of the OEC in photosystem II.
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| 8. |
- Pelling, S., et al.
(author)
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Point contact readout for a quantum dot terahertz sensor
- 2008
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In: Applied Physics Letters. - 0003-6951 .- 1077-3118. ; 93:7, s. 073501-
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Journal article (peer-reviewed)abstract
- We introduce a terahertz radiation sensor in which the photon-induced ionization state of a quantum dot is monitored by a point contact formed in the same semiconductor heterostructure. For comparison we used a readout based on a single electron transistor coupled to the same quantum dot. The experiments prove functionality of the point contact-based device with additional practical advantage of a higher operation temperature up to 1.5 K and ease of nanofabrication
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