| 1. |
- Antonov, A. N., et al.
(författare)
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The electron-ion scattering experiment ELISe at the International Facility for Antiproton and Ion Research (FAIR)-A conceptual design study
- 2011
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 0167-5087. ; 637:1, s. 60-76
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Tidskriftsartikel (refereegranskat)abstract
- The electron-ion scattering experiment ELISe is part of the installations envisaged at the new experimental storage ring at the International Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany. It offers an unique opportunity to use electrons as probe in investigations of the structure of exotic nuclei. The conceptual design and the scientific challenges of ELISe are presented. (C) 2011 Elsevier B.V. All rights reserved.
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| 2. |
- Reifarth, R., et al.
(författare)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Konferensbidrag (refereegranskat)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 3. |
- Ivanov, Maxim A., et al.
(författare)
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Preparation and structural organisation of heteroleptic tetraphenylantimony(V) complexes comprising unidentately and bidentately coordinated O,O'-dialkyldithiophosphate groups : multinuclear (C-13 P-31) CP/MAS NMR and single-crystal X-ray diffraction studies
- 2007
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693 .- 1873-3255. ; 360:9, s. 2897-2904
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Tidskriftsartikel (refereegranskat)abstract
- O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate (Dtph) tetraphenylantimony(V) complexes of the general formula [Sb(C6H5)4{S2P(OR)2}] (R = C3H7, i-C4H9) were prepared and studied by means of 13C, 31P CP/MAS NMR spectroscopy and single-crystal X-ray diffraction. Distorted octahedral and trigonal bipyramidal molecular structures have been established for prepared complexes. These unexpected structural distinctions between chemically related compounds are defined by the principally different coordination modes of O,O′-dipropyldithiophosphate and O,O′-di-iso-butyldithiophosphate ligands in their molecular structures (i.e., S,S′-bidentate chelating and S-unidentately coordinated, respectively). To characterise quantitatively phosphorus sites in both species of dithiophosphate ligands, 31P chemical shift anisotropy parameters (δaniso and η) were calculated from spinning sideband manifolds in MAS NMR spectra. The 31P chemical shift tensors for the bidentate chelating and unidentately coordinated dithiophosphate ligands display a profoundly rhombic and nearly axially symmetric characters, respectively.
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| 4. |
- Karnachuk, Olia V, et al.
(författare)
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Sulfate reduction potential in sediments in the Norilsk mining area, northern Siberia
- 2005
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Ingår i: Geomicrobiology Journal. - Philadelphia : Taylor & Francis. - 0149-0451 .- 1521-0529. ; 22:1-2, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to characterize the distribution and activity of sulfate-reducing bacteria in tailings and sediments impacted by effluents from mining and smelting operations in the Norilsk area in northern Siberia. The Norilsk mining complex involves three smelter operations, a hydrometallurgical plant, and extensive tailings areas located in the permafrost zone. Sulfate reduction rates measured with a (35)SO(4)(2-) tracer technique under various in-situ conditions ranged from 0.05 to 30 nmol S cm(-3) day(-1). Acetate and glucose addition greatly stimulated sulfate reduction, whereas lactate had less effect. The most pronounced stimulation of sulfate reduction (6.5-fold) was observed with phosphate amendment. Most-probable-number (MPN) counts of sulfate-reducing bacteria in media with glucose, ethanol, lactate, and acetate as electron donors were generally highest at around 10(7) cells ml(-1). The actual MPN counts varied with the sample, electron donor, and incubation conditions (pH 7.2 vs. pH 3.5; 28 degrees C vs. 4 degrees C). Enrichment cultures of sulfate-reducing bacteria were established from a sample that showed the highest rate of sulfate reduction. After multiple serial transfers, the dominant sulfate-reducers were identified by fluorescence in situ hybridization using genus and group-specific 16S rRNA-targeted oligonucleotide probes. Desulfobulbus spp. prevailed in ethanol and lactate enrichments and the Desulfosarcina-Desulfococcus group dominated in acetate and benzoate enrichments. Psychrophilic Desulfotalea-Desulfofustis and moderately psychrophilic Desulforhopalus spp. were identified in enrichments incubated at 4 degrees C, but they were also found in mesophilic enrichments.
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| 5. |
- Pozina, Galia, et al.
(författare)
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Nonlinear behavior of the emission in the periodic structure of InAs monolayers embedded in a GaAs matrix
- 2017
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Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951. ; 254:4
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (TRPL) measurements performed at different temperatures for the Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in a GaAs matrix. TRPL data reveal an appearance of the additional superradiant (SR) mode originated from coherent collective interaction of QWs. The SR mode is not manifested in the case if a small number of QWs is excited, then only an exciton emission related to the InAs QWs dominates the PL spectrum. The SR mode demonstrates a superlinear dependence of the intensity and radiative decay rate on the excitation power and its intensity increases at elevated temperatures compared to the excitonic emission. The photoluminescence delay time is much shorter for the SR mode indicating that the relaxation of hot excitons can occur via stimulated scattering processes. The specific behavior of the SR emission can have a strong potential for different applications such as optical logic devices, superluminescent diodes, optical switches, and low-threshold lasers. Time-resolved photoluminescence image at low temperature for the Bragg structure consisting of InAs monolayer-based quantum wells (inset).
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| 6. |
- Girshova, Elizaveta I, et al.
(författare)
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Proposal for a photoacoustic ultrasonic generator based on Tamm plasmon structures
- 2020
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 28:18, s. 26161-26169
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Tidskriftsartikel (refereegranskat)abstract
- The scheme of a generation of ultrasound waves based on optically excited Tamm plasmon structures is proposed. It is shown that Tamm plasmon structures can provide total absorption of a laser pulse with arbitrary wavelength in a metallic layer providing the possibility of the use of an infrared semiconductor laser for the excitation of ultrasound waves. Laser pulse absorption, heat transfer and dynamical properties of the structure are modeled, and the optimal design of the structure is found. It is demonstrated that the Tamm plasmon-based photoacoustic generator can emit ultrasound waves in the frequency band up to 100 MHz with predefined frequency spectrum. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
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| 7. |
- Morozov, Konstantin M., et al.
(författare)
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Efficient UV Luminescence from Organic-Based Tamm Plasmon Structures Emitting in the Strong-Coupling Regime
- 2020
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 124:39, s. 21656-21663
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Tidskriftsartikel (refereegranskat)abstract
- Excitons in organic semiconductors possessing a large oscillator strength demonstrate strong coupling with cavity modes at room temperature. A large Stokes shift in some organic semiconductors enriches and complicates the picture of the emission in strongly coupled systems of organic excitons and light. Here, we demonstrate strong coupling of excitons in 4,4-bis(N-carbazolyl)-1,1-biphenyl (CBP) and Tamm plasmons in the ultraviolet (UV) band, accompanied by a bright emission from the structure. Reflection measurements demonstrate the pronounced formation of the lower and upper polariton modes with Rabi splitting of the magnitude of 0.3 eV, and the emission peak experiences a substantial red shift with respect to the lower polariton mode. Both radiative and nonradiative decay rates in the Tamm plasmon CBP structure are increased with respect to a bare CBP. Such peculiar behavior is attributed to the simultaneous manifestation of strong coupling and weak coupling of the CBP molecule emitters to the Tamm plasmons.
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| 8. |
- Morozov, Konstantin M., et al.
(författare)
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Opposite Sign of Polarization Splitting in Ultrastrongly Coupled Organic Tamm Plasmon Structures
- 2021
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Ingår i: The Journal of Physical Chemistry C. - : AMER CHEMICAL SOC. - 1932-7447 .- 1932-7455. ; 125:15, s. 8376-8381
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Tidskriftsartikel (refereegranskat)abstract
- The properties of the ultrastrongly coupled Tamm plasmon cavity filled with a high-oscillator-strength organic material DPAVBi (4,4-bis[4-(di-p-tolylamino)styryl]biphenyl) are studied using theoretical and experimental methods. An analytical model predicts the opposite sign of polarization splitting for the lower and upper polariton cases and a giant absolute value of the splitting. A set of organic Tamm plasmon cavities with different detuning parameters are fabricated. We demonstrate that all structures are operating in the ultrastrong coupling regime: the values of the Rabi splitting are close to a 20% fraction of the exciton energy. The measured angle-dependent reflectivity spectra structure for both transverse electric (TE) and transverse magnetic (TM) polarizations confirm the predicted theoretical model. We obtained a giant value of the polarization splitting of up to 180 meV for both polariton branches. We believe that it is the first demonstration of such peculiar polarization splitting behavior of polaritons in the ultrastrong coupling regime.
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| 9. |
- Pozina, Galia, et al.
(författare)
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Emission Properties of GaN Planar Hexagonal Microcavities
- 2020
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Ingår i: Physica Status Solidi (a) applications and materials science. - : WILEY-V C H VERLAG GMBH. - 1862-6300 .- 1862-6319. ; 217:14
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Tidskriftsartikel (refereegranskat)abstract
- Fabrication of microcavities based on III-nitrides is challenging due to difficulties with the coherent growth of heterostructures having a large number of periods, at the same time keeping a good precision in terms of thickness and composition of the alloy. A planar design for GaN microresonators supporting whispering gallery modes is suggested. GaN hexagonal microstructures are fabricated by selective-area metalorganic vapor phase epitaxy using focused ion beam for mask patterning. Low-temperature cathodoluminescence spectra measured with a high spatial resolution demonstrate two dominant emission lines in the near bandgap region. These lines merge at room temperature into a broad emission band peaking at approximate to 3.3 eV, which is shifted toward lower energies compared with the reference excitonic spectrum measured for the GaN layer. A numerical analysis of exciton-polariton modes shows that some strongly localized cavity modes can have high Purcell coefficients and can strongly interact with the GaN exciton.
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| 10. |
- Pozina, Galia, et al.
(författare)
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Optical Cavity Based on GaN Planar Nanowires Grown by Selective Area Metal-Organic Vapor Phase Epitaxy
- 2019
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Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951. ; 256:6
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Tidskriftsartikel (refereegranskat)abstract
- GaN planar nanowires (NWs) are fabricated by selective area metal-organic vapor phase epitaxy using focused ion beam etching of trench pattern in the Si3N4 mask. Two crystallographic orientations of NWs along [1120] and [1010] directions are investigated. The coherent growth is confirmed for both directions; however, the best morphology, crystalline and optical properties are found in the GaN planar NWs fabricated along the [1010] axis. Cathodoluminescence (CL) at 5K reveals a presence of Fabry-Perot modes in the region of 1.8-2.5 eV for the NWs fabricated in the [1010] direction. The position and intensity of the Fabry-Perot peaks vary depending on measured point within the NW, which is explained by the model based on the Purcell coefficient calculations. It is shown that small fluctuations in the NW thickness cause a noticeable shift of the Fabry-Perot modes energies, while the enhancement or reduction of the emission intensity for the Fabry-Perot peaks depend on the position of the emitter inside the planar NW.
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| 11. |
- Duffy, J. Emmett, et al.
(författare)
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A Pleistocene legacy structures variation in modern seagrass ecosystems
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:32
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Tidskriftsartikel (refereegranskat)abstract
- Distribution of Earth's biomes is structured by the match between climate and plant traits, which in turn shape associated communities and ecosystem processes and services. However, that climate-trait match can be disrupted by historical events, with lasting ecosystem impacts. As Earth's environment changes faster than at any time in human history, critical questions are whether and how organismal traits and ecosystems can adjust to altered conditions. We quantified the relative importance of current environmental forcing versus evolutionary history in shaping the growth form (stature and biomass) and associated community of eelgrass (Zostera marina), a widespread foundation plant of marine ecosystems along Northern Hemisphere coastlines, which experienced major shifts in distribution and genetic composition during the Pleistocene. We found that eelgrass stature and biomass retain a legacy of the Pleistocene colonization of the Atlantic from the ancestral Pacific range and of more recent within-basin bottlenecks and genetic differentiation. This evolutionary legacy in turn influences the biomass of associated algae and invertebrates that fuel coastal food webs, with effects comparable to or stronger than effects of current environmental forcing. Such historical lags in phenotypic acclimatization may constrain ecosystem adjustments to rapid anthropogenic climate change, thus altering predictions about the future functioning of ecosystems.
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| 12. |
- Ivanov, Mikhail, et al.
(författare)
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Thermal unwinding of Polyadenylic center dot Polyuridylic acid complex with TMPyP4 porphyrin in aqueous solutions
- 2020
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0022-2860 .- 1872-8014. ; 1202
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Tidskriftsartikel (refereegranskat)abstract
- The molecular mechanism of Poly(A)center dot Poly(U) (Polyadenylic center dot Polyuridylic acid) polyribonucleotide denaturation was studied through a combination of molecular dynamics (MD) simulations and UV-Vis-melting experiments. UV-Vis absorption spectra of Poly(A)center dot Poly(U) were measured at different temperatures (20-70 degrees C) both in the absence and presence of porphyrin-ligand TMPyP4 in equilibrated aqueous solutions (pH 7.0). Thermal behavior of double-stranded structure of Poly(A)center dot Poly(U) altered by formation of the ternary [Poly(A)center dot Poly(U)]*(TMPyP4)(n) complexes was studied with the help of a new semi-soft chemometrics procedure, based on the analyses of fractions of species in solution versus temperature. The melting temperature in the presence of porphyrin is 1.2 degrees C higher than that for pure polyribonucleotide, which indicates that porphyrin binding contributes to the suppression of transition between the native ordered structure of Poly(A)center dot Poly(U) and disordered state. MD simulations were performed for the binding of TMPyP4 to (rA)(12)center dot(rU)(12) oligonucleotide to provide molecular-level insight into the mechanism of duplex dsRNA melting in the presence of TMPyP4. The results of MD simulations suggest a molecular mechanism of thermal stabilization of the native structure through the accommodation of TMPyP4 in double-stranded structure of (rA)(12)center dot(rU)(12) oligonucleotide groove close to the end of the ordered region of stacked nucleobase pairs.
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| 13. |
- Vandaele, Ann Carine, et al.
(författare)
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Martian dust storm impact on atmospheric H2O and D/H observed by ExoMars Trace Gas Orbiter
- 2019
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Ingår i: Nature. - : Springer. - 1476-4687 .- 1476-4687 .- 0028-0836. ; 568:7753, s. 521-525
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Global dust storms on Mars are rare1,2 but can affect the Martian atmosphere for several months. They can cause changes in atmospheric dynamics and inflation of the atmosphere3, primarily owing to solar heating of the dust3. In turn, changes in atmospheric dynamics can affect the distribution of atmospheric water vapour, with potential implications for the atmospheric photochemistry and climate on Mars4. Recent observations of the water vapour abundance in the Martian atmosphere during dust storm conditions revealed a high-altitude increase in atmospheric water vapour that was more pronounced at high northern latitudes5,6, as well as a decrease in the water column at low latitudes7,8. Here we present concurrent, high-resolution measurements of dust, water and semiheavy water (HDO) at the onset of a global dust storm, obtained by the NOMAD and ACS instruments onboard the ExoMars Trace Gas Orbiter. We report the vertical distribution of the HDO/H2O ratio (D/H) from the planetary boundary layer up to an altitude of 80 kilometres. Our findings suggest that before the onset of the dust storm, HDO abundances were reduced to levels below detectability at altitudes above 40 kilometres. This decrease in HDO coincided with the presence of water-ice clouds. During the storm, an increase in the abundance of H2O and HDO was observed at altitudes between 40 and 80 kilometres. We propose that these increased abundances may be the result of warmer temperatures during the dust storm causing stronger atmospheric circulation and preventing ice cloud formation, which may confine water vapour to lower altitudes through gravitational fall and subsequent sublimation of ice crystals3. The observed changes in H2O and HDO abundance occurred within a few days during the development of the dust storm, suggesting a fast impact of dust storms on the Martian atmosphere.
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