104,406 results on '"Bo B"'
Search Results
2. Direct observation of one-dimensional disordered diffusion channel in a chain-like thermoelectric with ultralow thermal conductivity
- Author
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Jiawei Zhang, Nikolaj Roth, Kasper Tolborg, Seiya Takahashi, Lirong Song, Martin Bondesgaard, Eiji Nishibori, and Bo B. Iversen
- Subjects
Science - Abstract
Disordered, diffusive atoms are rarely found in simple crystalline solids. Here, the authors observe one-dimensional disordered diffusion channel in a simple chain-like thermoelectric InTe with ultralow thermal conductivity.
- Published
- 2021
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3. Tuneable local order in thermoelectric crystals
- Author
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Nikolaj Roth, Jonas Beyer, Karl F. F. Fischer, Kaiyang Xia, Tiejun Zhu, and Bo B. Iversen
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local order ,diffuse scattering ,thermoelectrics ,hidden phases ,Crystallography ,QD901-999 - Abstract
Although crystalline solids are characterized by their periodic structures, some are only periodic on average and deviate on a local scale. Such disordered crystals with distinct local structures have unique properties arising from both collective and localized behaviour. Different local orderings can exist with identical average structures, making their differences hidden to Bragg diffraction methods. Using high-quality single-crystal X-ray diffuse scattering the local order in thermoelectric half-Heusler Nb1−xCoSb is investigated, for which different local orderings are observed. It is shown that the vacancy distribution follows a vacancy repulsion model and the crystal composition is found always to be close to x = 1/6 irrespective of nominal sample composition. However, the specific synthesis method controls the local order and thereby the thermoelectric properties thus providing a new frontier for tuning material properties.
- Published
- 2021
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4. Structural evolution in thermoelectric zinc antimonide thin films studied by in situ X-ray scattering techniques
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Lirong Song, Martin Roelsgaard, Anders B. Blichfeld, Ann-Christin Dippel, Kirsten Marie Ørnsbjerg Jensen, Jiawei Zhang, and Bo B. Iversen
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zinc antimonide thin films ,structural evolution ,in situ x-ray diffraction ,in situ x-ray total scattering ,Crystallography ,QD901-999 - Abstract
Zinc antimonides have been widely studied owing to their outstanding thermoelectric properties. Unlike in the bulk state, where various structurally unknown phases have been identified through their specific physical properties, a number of intermediate phases in the thin-film state remain largely unexplored. Here, in situ X-ray diffraction and X-ray total scattering are combined with in situ measurement of electrical resistivity to monitor the crystallization process of as-deposited amorphous Zn-Sb films during post-deposition annealing. The as-deposited Zn-Sb films undergo a structural evolution from an amorphous phase to an intermediate crystalline phase and finally the ZnSb phase during heat treatment up to 573 K. An intermediate phase (phase B) is identified to be a modified β-Zn8Sb7 phase by refinement of the X-ray diffraction data. Within a certain range of Sb content (∼42–55 at%) in the films, phase B is accompanied by an emerging Sb impurity phase. Lower Sb content leads to smaller amounts of Sb impurity and the formation of phase B at lower temperatures, and phase B is stable at room temperature if the annealing temperature is controlled. Pair distribution function analysis of the amorphous phase shows local ordered units of distorted ZnSb4 tetrahedra, and annealing leads to long-range ordering of these units to form the intermediate phase. A higher formation energy is required when the intermediate phase evolves into the ZnSb phase with a significantly more regular arrangement of ZnSb4 tetrahedra.
- Published
- 2021
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5. A simple model for vacancy order and disorder in defective half-Heusler systems
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Nikolaj Roth, Tiejun Zhu, and Bo B. Iversen
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defective half-heuslers ,diffuse scattering ,short-range order ,correlated disorder ,thermoelectrics ,inorganic materials ,materials modeling ,properties of solids ,Crystallography ,QD901-999 - Abstract
Defective half-Heusler systems X1−xYZ with large amounts of intrinsic vacancies, such as Nb1−xCoSb, Ti1−xNiSb and V1−xCoSb, are a group of promising thermoelectric materials. Even with high vacancy concentrations they maintain the average half-Heusler crystal structure. These systems show high electrical conductivity but low thermal conductivity arising from an ordered YZ substructure, which conducts electrons, while the large amounts of vacancies in the X substructure effectively scatters phonons. Using electron scattering, it was recently observed that, in addition to Bragg diffraction from the average cubic half-Heusler structure, some of these samples show broad diffuse scattering indicating short-range vacancy order, while other samples show sharp additional peaks indicating long-range vacancy ordering. Here it is shown that both the short- and long-range ordering can be explained using the same simple model, which assumes that vacancies in the X substructure avoid each other. The samples showing long-range vacancy order are in agreement with the predicted ground state of the model, while short-range order samples are quenched high-temperature states of the system. A previous study showed that changes in sample stoichiometry affect whether the short- or long-range vacancy structure is obtained, but the present model suggests that thermal treatment of samples should allow controlling the degree of vacancy order, and thereby the thermal conductivity, without changes in composition. This is important as the composition also dictates the amount of electrical carriers. Independent control of electrical carrier concentration and degree of vacancy order should allow further improvements in the thermoelectric properties of these systems.
- Published
- 2020
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6. Expression and interactions of stereochemically active lone pairs and their relation to structural distortions and thermal conductivity
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Kasper Tolborg, Carlo Gatti, and Bo B. Iversen
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lone pairs ,chemical bonding ,thermal conductivity ,quantum crystallography ,electron densities ,Crystallography ,QD901-999 - Abstract
In chemistry, stereochemically active lone pairs are typically described as an important non-bonding effect, and recent interest has centred on understanding the derived effect of lone pair expression on physical properties such as thermal conductivity. To manipulate such properties, it is essential to understand the conditions that lead to lone pair expression and provide a quantitative chemical description of their identity to allow comparison between systems. Here, density functional theory calculations are used first to establish the presence of stereochemically active lone pairs on antimony in the archetypical chalcogenide MnSb2O4. The lone pairs are formed through a similar mechanism to those in binary post-transition metal compounds in an oxidation state of two less than their main group number [e.g. Pb(II) and Sb(III)], where the degree of orbital interaction (covalency) determines the expression of the lone pair. In MnSb2O4 the Sb lone pairs interact through a void space in the crystal structure, and their their mutual repulsion is minimized by introducing a deflection angle. This angle increases significantly with decreasing Sb—Sb distance introduced by simulating high pressure, thus showing the highly destabilizing nature of the lone pair interactions. Analysis of the chemical bonding in MnSb2O4 shows that it is dominated by polar covalent interactions with significant contributions both from charge accumulation in the bonding regions and from charge transfer. A database search of related ternary chalcogenide structures shows that, for structures with a lone pair (SbX3 units), the degree of lone pair expression is largely determined by whether the antimony–chalcogen units are connected or not, suggesting a cooperative effect. Isolated SbX3 units have larger X—Sb—X bond angles and therefore weaker lone pair expression than connected units. Since increased lone pair expression is equivalent to an increased orbital interaction (covalent bonding), which typically leads to increased heat conduction, this can explain the previously established correlation between larger bond angles and lower thermal conductivity. Thus, it appears that for these chalcogenides, lone pair expression and thermal conductivity may be related through the degree of covalency of the system.
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- 2020
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7. Evolution of the Polymorph Selectivity of Titania Formation under Acidic and Low-Temperature Conditions
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Gunnar Símonarson, Sanna Sommer, Antiope Lotsari, Björn Elgh, Bo B. Iversen, and Anders E.C. Palmqvist
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Chemistry ,QD1-999 - Published
- 2019
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8. Probing the accuracy and precision of Hirshfeld atom refinement with HARt interfaced with Olex2
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Malte Fugel, Dylan Jayatilaka, Emanuel Hupf, Jacob Overgaard, Venkatesha R. Hathwar, Piero Macchi, Michael J. Turner, Judith A. K. Howard, Oleg V. Dolomanov, Horst Puschmann, Bo B. Iversen, Hans-Beat Bürgi, and Simon Grabowsky
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Hirshfeld atom refinement ,multipole modelling ,anisotropic displacement parameters ,hydrogen-atom properties ,crystallographic software ,Crystallography ,QD901-999 - Abstract
Hirshfeld atom refinement (HAR) is a novel X-ray structure refinement technique that employs aspherical atomic scattering factors obtained from stockholder partitioning of a theoretically determined tailor-made static electron density. HAR overcomes many of the known limitations of independent atom modelling (IAM), such as too short element–hydrogen distances, r(X—H), or too large atomic displacement parameters (ADPs). This study probes the accuracy and precision of anisotropic hydrogen and non-hydrogen ADPs and of r(X—H) values obtained from HAR. These quantities are compared and found to agree with those obtained from (i) accurate neutron diffraction data measured at the same temperatures as the X-ray data and (ii) multipole modelling (MM), an established alternative method for interpreting X-ray diffraction data with the help of aspherical atomic scattering factors. Results are presented for three chemically different systems: the aromatic hydrocarbon rubrene (orthorhombic 5,6,11,12-tetraphenyltetracene), a co-crystal of zwitterionic betaine, imidazolium cations and picrate anions (BIPa), and the salt potassium hydrogen oxalate (KHOx). The non-hydrogen HAR-ADPs are as accurate and precise as the MM-ADPs. Both show excellent agreement with the neutron-based values and are superior to IAM-ADPs. The anisotropic hydrogen HAR-ADPs show a somewhat larger deviation from neutron-based values than the hydrogen SHADE-ADPs used in MM. Element–hydrogen bond lengths from HAR are in excellent agreement with those obtained from neutron diffraction experiments, although they are somewhat less precise. The residual density contour maps after HAR show fewer features than those after MM. Calculating the static electron density with the def2-TZVP basis set instead of the simpler def2-SVP one does not improve the refinement results significantly. All HARs were performed within the recently introduced HARt option implemented in the Olex2 program. They are easily launched inside its graphical user interface following a conventional IAM.
- Published
- 2018
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9. Crystal structure across the β to α phase transition in thermoelectric Cu2−xSe
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Espen Eikeland, Anders B. Blichfeld, Kasper A. Borup, Kunpeng Zhao, Jacob Overgaard, Xun Shi, Lidong Chen, and Bo B. Iversen
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thermoelectrics ,negative thermal expansion ,properties of solids ,inorganic materials ,Crystallography ,QD901-999 - Abstract
The crystal structure uniquely imparts the specific properties of a material, and thus provides the starting point for any quantitative understanding of thermoelectric properties. Cu2−xSe is an intensely studied high performing, non-toxic and cheap thermoelectric material, and here for the first time, the average structure of β-Cu2−xSe is reported based on analysis of multi-temperature single-crystal X-ray diffraction data. It consists of Se–Cu layers with additional copper between every alternate layer. The structural changes during the peculiar zT enhancing phase transition mainly consist of changes in the inter-layer distance coupled with subtle Cu migration. Just prior to the transition the structure exhibits strong negative thermal expansion due to the reordering of Cu atoms, when approached from low temperatures. The phase transition is fully reversible and group–subgroup symmetry relations are derived that relate the low-temperature β-phase to the high-temperature α-phase. Weak superstructure reflections are observed and a possible Cu ordering is proposed. The structural rearrangement may have a significant impact on the band structure and the Cu rearrangement may also be linked to an entropy increase. Both factors potentially contribute to the extraordinary zT enhancement across the phase transition.
- Published
- 2017
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10. Designing high-performance layered thermoelectric materials through orbital engineering
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Jiawei Zhang, Lirong Song, Georg K. H. Madsen, Karl F. F. Fischer, Wenqing Zhang, Xun Shi, and Bo B. Iversen
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Science - Abstract
Thermoelectric materials with enhanced performances need to be identified. Here, the authors use the crystal field splitting energy of orbitals as a descriptor to design thermoelectric materials by solid solution maps and strain engineering in layered CaAl2Si2-type Zintl compounds.
- Published
- 2016
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11. Single-Cell Genomics Reveals a Diverse Metabolic Potential of Uncultivated Desulfatiglans-Related Deltaproteobacteria Widely Distributed in Marine Sediment
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Lara M. Jochum, Lars Schreiber, Ian P. G. Marshall, Bo B. Jørgensen, Andreas Schramm, and Kasper U. Kjeldsen
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single cell genomics ,Desulfarculaceae ,acetogenesis ,dissimilatory sulfate reduction ,aromatic compounds degradation ,dehalogenation ,Microbiology ,QR1-502 - Abstract
Desulfatiglans-related organisms comprise one of the most abundant deltaproteobacterial lineages in marine sediments where they occur throughout the sediment column in a gradient of increasing sulfate and organic carbon limitation with depth. Characterized Desulfatiglans isolates are dissimilatory sulfate reducers able to grow by degrading aromatic hydrocarbons. The ecophysiology of environmental Desulfatiglans-populations is poorly understood, however, possibly utilization of aromatic compounds may explain their predominance in marine subsurface sediments. We sequenced and analyzed seven Desulfatiglans-related single-cell genomes (SAGs) from Aarhus Bay sediments to characterize their metabolic potential with regard to aromatic compound degradation and energy metabolism. The average genome assembly size was 1.3 Mbp and completeness estimates ranged between 20 and 50%. Five of the SAGs (group 1) originated from the sulfate-rich surface part of the sediment while two (group 2) originated from sulfate-depleted subsurface sediment. Based on 16S rRNA gene amplicon sequencing group 2 SAGs represent the more frequent types of Desulfatiglans-populations in Aarhus Bay sediments. Genes indicative of aromatic compound degradation could be identified in both groups, but the two groups were metabolically distinct with regard to energy conservation. Group 1 SAGs carry a full set of genes for dissimilatory sulfate reduction, whereas the group 2 SAGs lacked any genetic evidence for sulfate reduction. The latter may be due to incompleteness of the SAGs, but as alternative energy metabolisms group 2 SAGs carry the genetic potential for growth by acetogenesis and fermentation. Group 1 SAGs encoded reductive dehalogenase genes, allowing them to access organohalides and possibly conserve energy by their reduction. Both groups possess sulfatases unlike their cultured relatives allowing them to utilize sulfate esters as source of organic carbon and sulfate. In conclusion, the uncultivated marine Desulfatiglans populations are metabolically diverse, likely reflecting different strategies for coping with energy and sulfate limitation in the subsurface seabed.
- Published
- 2018
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12. Sulfate Transporters in Dissimilatory Sulfate Reducing Microorganisms: A Comparative Genomics Analysis
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Angeliki Marietou, Hans Røy, Bo B. Jørgensen, and Kasper U. Kjeldsen
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sulfate transporter ,sulfate-reducing microorganisms ,SulP ,CysP ,CysZ ,DASS ,Microbiology ,QR1-502 - Abstract
The first step in the sulfate reduction pathway is the transport of sulfate across the cell membrane. This uptake has a major effect on sulfate reduction rates. Much of the information available on sulfate transport was obtained by studies on assimilatory sulfate reduction, where sulfate transporters were identified among several types of protein families. Despite our growing knowledge on the physiology of dissimilatory sulfate-reducing microorganisms (SRM) there are no studies identifying the proteins involved in sulfate uptake in members of this ecologically important group of anaerobes. We surveyed the complete genomes of 44 sulfate-reducing bacteria and archaea across six phyla and identified putative sulfate transporter encoding genes from four out of the five surveyed protein families based on homology. We did not find evidence that ABC-type transporters (SulT) are involved in the uptake of sulfate in SRM. We speculate that members of the CysP sulfate transporters could play a key role in the uptake of sulfate in thermophilic SRM. Putative CysZ-type sulfate transporters were present in all genomes examined suggesting that this overlooked group of sulfate transporters might play a role in sulfate transport in dissimilatory sulfate reducers alongside SulP. Our in silico analysis highlights several targets for further molecular studies in order to understand this key step in the metabolism of SRMs.
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- 2018
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13. Demonstration of thin film pair distribution function analysis (tfPDF) for the study of local structure in amorphous and crystalline thin films
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Kirsten M. Ø. Jensen, Anders B. Blichfeld, Sage R. Bauers, Suzannah R. Wood, Eric Dooryhée, David C. Johnson, Bo B. Iversen, and Simon J. L. Billinge
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total scattering ,pair distribution function analysis ,thin films ,framework-structured solids and amorphous materials ,inorganic materials ,materials modelling ,nanostructure ,amorphous solids ,Crystallography ,QD901-999 - Abstract
By means of normal-incidence, high-flux and high-energy X-rays, total scattering data for pair distribution function (PDF) analysis have been obtained from thin films (tf), suitable for local structure analysis. By using amorphous substrates as support for the films, the standard Rapid Acquisition PDF setup can be applied and the scattering signal from the film can be isolated from the total scattering data through subtraction of an independently measured background signal. No angular corrections to the data are needed, as would be the case for grazing incidence measurements. The `tfPDF' method is illustrated through studies of as-deposited (i.e. amorphous) and crystalline FeSb3 films, where the local structure analysis gives insight into the stabilization of the metastable skutterudite FeSb3 phase. The films were prepared by depositing ultra-thin alternating layers of Fe and Sb, which interdiffuse and after annealing crystallize to form the FeSb3 structure. The tfPDF data show that the amorphous precursor phase consists of corner-sharing FeSb6 octahedra with motifs highly resembling the local structure in crystalline FeSb3. Analysis of the amorphous structure allows the prediction of whether the final crystalline product will form the FeSb3 phase with or without excess Sb present. The study thus illustrates how analysis of the local structure in amorphous precursor films can help to understand crystallization processes of metastable phases and opens for a range of new local structure studies of thin films.
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- 2015
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14. Concurrent Methane Production and Oxidation in Surface Sediment from Aarhus Bay, Denmark
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Ke-Qing Xiao, Felix Beulig, Kasper U. Kjeldsen, Bo B. Jørgensen, and Nils Risgaard-Petersen
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methanogenesis ,methane oxidation ,surface sediment ,methanogenic archaea ,isotope dilution ,Microbiology ,QR1-502 - Abstract
Marine surface sediments, which are replete with sulfate, are typically considered to be devoid of endogenous methanogenesis. Yet, methanogenic archaea are present in those sediments, suggesting a potential for methanogenesis. We used an isotope dilution method based on sediment bag incubation and spiking with 13C-CH4 to quantify CH4 turnover rates in sediment from Aarhus Bay, Denmark. In two independent experiments, highest CH4 production and oxidation rates (>200 pmol cm-3 d-1) were found in the top 0–2 cm, below which rates dropped below 100 pmol cm-3 d-1 in all other segments down to 16 cm. This drop in overall methane turnover with depth was accompanied by decreasing rates of organic matter mineralization with depth. Molecular analyses based on quantitative PCR and MiSeq sequencing of archaeal 16S rRNA genes showed that the abundance of methanogenic archaea also peaked in the top 0–2 cm segment. Based on the community profiling, hydrogenotrophic and methylotrophic methanogens dominated among the methanogenic archaea in general, suggesting that methanogenesis in surface sediment could be driven by both CO2 reduction and fermentation of methylated compounds. Our results show the existence of elevated methanogenic activity and a dynamic recycling of CH4 at low concentration in sulfate-rich marine surface sediment. Considering the common environmental conditions found in other coastal systems, we speculate that such a cryptic methane cycling can be ubiquitous.
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- 2017
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15. Contemporary X-ray electron-density studies using synchrotron radiation
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Mads R. V. Jørgensen, Venkatesha R. Hathwar, Niels Bindzus, Nanna Wahlberg, Yu-Sheng Chen, Jacob Overgaard, and Bo B. Iversen
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electron-density studies ,synchrotron radiation ,X-ray diffraction ,Crystallography ,QD901-999 - Abstract
Synchrotron radiation has many compelling advantages over conventional radiation sources in the measurement of accurate Bragg diffraction data. The variable photon energy and much higher flux may help to minimize critical systematic effects such as absorption, extinction and anomalous scattering. Based on a survey of selected published results from the last decade, the benefits of using synchrotron radiation in the determination of X-ray electron densities are discussed, and possible future directions of this field are examined.
- Published
- 2014
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16. Evolution of atomic structure during nanoparticle formation
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Christoffer Tyrsted, Nina Lock, Kirsten M. Ø. Jensen, Mogens Christensen, Espen D. Bøjesen, Hermann Emerich, Gavin Vaughan, Simon J. L. Billinge, and Bo B. Iversen
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total scattering ,EXAFS ,PDF ,in situ ,nanoparticle ,Crystallography ,QD901-999 - Abstract
Understanding the mechanism of nanoparticle formation during synthesis is a key prerequisite for the rational design and engineering of desirable materials properties, yet remains elusive due to the difficulty of studying structures at the nanoscale under real conditions. Here, the first comprehensive structural description of the formation of a nanoparticle, yttria-stabilized zirconia (YSZ), all the way from its ionic constituents in solution to the final crystal, is presented. The transformation is a complicated multi-step sequence of atomic reorganizations as the material follows the reaction pathway towards the equilibrium product. Prior to nanoparticle nucleation, reagents reorganize into polymeric species whose structure is incompatible with the final product. Instead of direct nucleation of clusters into the final product lattice, a highly disordered intermediate precipitate forms with a local bonding environment similar to the product yet lacking the correct topology. During maturation, bond reforming occurs by nucleation and growth of distinct domains within the amorphous intermediary. The present study moves beyond kinetic modeling by providing detailed real-time structural insight, and it is demonstrated that YSZ nanoparticle formation and growth is a more complex chemical process than accounted for in conventional models. This level of mechanistic understanding of the nanoparticle formation is the first step towards more rational control over nanoparticle synthesis through control of both solution precursors and reaction intermediaries.
- Published
- 2014
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17. Machine learning based approach for solving atomic structures of nanomaterials combining pair distribution functions with density functional theory
- Author
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Kløve, Magnus, Sommer, Sanna, Iversen, Bo B., Hammer, Bjørk, and Dononelli, Wilke
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Condensed Matter - Materials Science - Abstract
Determination of crystal structures of nanocrystalline or amorphous compounds is a great challenge in solid states chemistry and physics. Pair distribution function (PDF) analysis of X-Ray or neutron total scattering data has proven to be a key element in tackling this challenge. However, in most cases a reliable structural motif is needed as starting configuration for structure refinements. Here, we present an algorithm that is able to determine the crystal structure of an unknown compound by means of an on-the-fly trained machine learning model that combines density functional theory (DFT) calculations with comparison of calculated and measured PDFs for global optimization in an artificial landscape. Due to the nature of this landscape, even metastable configurations can be determined.
- Published
- 2022
18. Changes of pH in β-Lactoglobulin and β-Casein Solutions during High Pressure Treatment
- Author
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Karsten Olsen, Bo B. Jespersen, and Vibeke Orlien
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Optics. Light ,QC350-467 - Abstract
The pH changes in the milk systems, β-lactoglobulin B, β-casein, and mixture of β-lactoglobulin and β-casein (pH 7 and ionic strength 0.08 M) were measured in situ during increasing pressure up to 500 MPa. An initial decrease to pH 6.7 was observed from 0.1 to 150 MPa for β-lactoglobulin, followed by an increase to pH 7.3 at 500 MPa. The initial decrease is suggested to be caused by the deprotonation of histidine, while the increase is suggested to result from an increase of hydroxide ions due to the loss of tertiary structure. The change in pH of the β-casein solution displayed an almost linear increasing pressure dependency up to a pH of 7.7 at 500 MPa. The limited tertiary structure of β-casein could allow exposure of all amino acids; thus the increase of pH can be caused by binding of water protons resulting in an increase of hydroxide ions. Addition of β-casein to β-lactoglobulin (1:1) was found to suppress the initial pH decrease found for the β-lactoglobulin solution. The pH change of the mixture did not suggest any intermolecular interaction, and a simple additive model is proposed to calculate the pH change of the mixture from the corresponding individual samples.
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- 2015
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19. Phase transition enhanced thermoelectric figure-of-merit in copper chalcogenides
- Author
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David R. Brown, Tristan Day, Kasper A. Borup, Sebastian Christensen, Bo B. Iversen, and G. Jeffrey Snyder
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Biotechnology ,TP248.13-248.65 ,Physics ,QC1-999 - Abstract
While thermoelectric materials can be used for solid state cooling, waste heat recovery, and solar electricity generation, low values of the thermoelectric figure of merit, zT, have led to an efficiency too low for widespread use. Thermoelectric effects are characterized by the Seebeck coefficient or thermopower, which is related to the entropy associated with charge transport. For example, coupling spin entropy with the presence of charge carriers has enabled the enhancement of zT in cobalt oxides. We demonstrate that the coupling of a continuous phase transition to carrier transport in Cu2Se over a broad (360–410 K) temperature range results in a dramatic peak in thermopower, an increase in phonon and electron scattering, and a corresponding doubling of zT (to 0.7 at 406 K), and a similar but larger increase over a wider temperature range in the zT of Cu1.97Ag.03Se (almost 1.0 at 400 K). The use of structural entropy for enhanced thermopower could lead to new engineering approaches for thermoelectric materials with high zT and new green applications for thermoelectrics.
- Published
- 2013
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20. Highly Selective Deethylation of Rhodamine B on Prepared in Supercritical Fluids
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Yuzun Fan, Guoping Chen, Dongmei Li, Yanhong Luo, Nina Lock, Anca Paduraru Jensen, Aref Mamakhel, Jianli Mi, Steen B. Iversen, Qingbo Meng, and Bo B. Iversen
- Subjects
Renewable energy sources ,TJ807-830 - Abstract
Pure phase anatase TiO2 nanoparticles with sizes of 5–8 nm and varying crystallinity were synthesized in supercritical isopropanol/water using a continuous flow reactor. Their photodegradation of rhodamine B (RhB) was evaluated under visible light irradiation. The as-prepared TiO2 nanoparticles show much higher photodegradation efficiencies than commercial Degussa P25 TiO2. Moreover, the photodegradation of RhB on the as-prepared TiO2 follows a different process from that on P25 TiO2, quicker N-deethylation and slower cleavage of conjugated chromophore structure. Based on PXRD, TEM, and BET measurements, these two photodegradation properties have been explained by the physicochemical properties of TiO2.
- Published
- 2012
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21. trans-Dibromidobis(1-ethyl-3-methylimidazol-2-ylidene)palladium(II)
- Author
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Solveig R. Madsen, Nina Lock, Jacob Overgaard, and Bo B. Iversen
- Subjects
Crystallography ,QD901-999 - Abstract
The title compound, trans-[PdBr2(C6H10N2)2], was synthesized ionothermally in the ionic liquid solvent 1-ethyl-3-methylimidazolium bromide. In the crystal, the PdII atoms are square-planarly coordinated to two Br atoms and two neutral (C6H10N2) ligands. The PdII atom is located on an inversion centre.
- Published
- 2011
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22. Identifying Racial and Ethnic Disparities in Acute Inpatient Rehabilitation
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Herrmann, Amanda A., Podgorski, Bo B., Hatton, Sarah J., Chrenka, Ella A., Hanson, Leah R., and Jackson, Steven D.
- Published
- 2024
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23. Insights into the genome of large sulfur bacteria revealed by analysis of single filaments.
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Marc Mussmann, Fen Z Hu, Michael Richter, Dirk de Beer, André Preisler, Bo B Jørgensen, Marcel Huntemann, Frank Oliver Glöckner, Rudolf Amann, Werner J H Koopman, Roger S Lasken, Benjamin Janto, Justin Hogg, Paul Stoodley, Robert Boissy, and Garth D Ehrlich
- Subjects
Biology (General) ,QH301-705.5 - Abstract
Marine sediments are frequently covered by mats of the filamentous Beggiatoa and other large nitrate-storing bacteria that oxidize hydrogen sulfide using either oxygen or nitrate, which they store in intracellular vacuoles. Despite their conspicuous metabolic properties and their biogeochemical importance, little is known about their genetic repertoire because of the lack of pure cultures. Here, we present a unique approach to access the genome of single filaments of Beggiatoa by combining whole genome amplification, pyrosequencing, and optical genome mapping. Sequence assemblies were incomplete and yielded average contig sizes of approximately 1 kb. Pathways for sulfur oxidation, nitrate and oxygen respiration, and CO2 fixation confirm the chemolithoautotrophic physiology of Beggiatoa. In addition, Beggiatoa potentially utilize inorganic sulfur compounds and dimethyl sulfoxide as electron acceptors. We propose a mechanism of vacuolar nitrate accumulation that is linked to proton translocation by vacuolar-type ATPases. Comparative genomics indicates substantial horizontal gene transfer of storage, metabolic, and gliding capabilities between Beggiatoa and cyanobacteria. These capabilities enable Beggiatoa to overcome non-overlapping availabilities of electron donors and acceptors while gliding between oxic and sulfidic zones. The first look into the genome of these filamentous sulfur-oxidizing bacteria substantially deepens the understanding of their evolution and their contribution to sulfur and nitrogen cycling in marine sediments.
- Published
- 2007
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24. On single crystal total scattering data reduction and correction protocols for analysis in direct space
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Koch, Robert J., Roth, Nikolaj, Liu, Yiu, Ivashko, Oleh, Dippel, Ann-Christin, Petrovic, Cedomir, Iversen, Bo B., Zimmermann, Martin v., and Bozin, Emil S.
- Subjects
Condensed Matter - Materials Science - Abstract
We explore data reduction and correction steps and processed data reproducibility in the emerging single crystal total scattering based technique of three-dimensional differential atomic pair distribution function (3D-$\Delta$PDF) analysis. All steps from sample measurement to data-processing are outlined in detail using a CuIr$_2$S$_4$ example crystal studied in a setup equipped with a high-energy x-ray beam and a flat panel area detector. Computational overhead as it pertains to data-sampling and the associated data processing steps is also discussed. Various aspects of the final 3D-$\Delta$PDF reproducibility are explicitly tested by varying data-processing order and included steps, and by carrying out a crystal-to-crystal data comparison. We identify situations in which the 3D-$\Delta$PDF is robust, and caution against a few particular cases which can lead to inconsistent 3D-$\Delta$PDFs. Although not all the approaches applied here-in will be valid across all systems, and a more in-depth analysis of some of the effects of the data processing steps may still needed, the methods collected here-in represent the start of a more systematic discussion about data processing and corrections in this field.
- Published
- 2021
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25. Chemical bonding origin of the thermoelectric power factor in Half-Heusler semiconductors
- Author
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Tolborg, Kasper and Iversen, Bo B.
- Subjects
Condensed Matter - Materials Science - Abstract
Intermetallic semiconductors with the cubic Half-Heusler structure (XYZ) have excellent thermoelectric properties. This has been attributed to the high degeneracy of the carrier pockets in the band structure, but large differences are found between different material compositions. Half-Heuslers are often interpreted within Zintl chemistry, making a clear distinction between an electropositive cation ($X^{n+}$) and an extended polyanion ($YZ^{n-}$). Based on quantitative real space chemical bonding analysis, we unravel large degrees of covalent bonding between the formal cation and anion, making the Zintl distinction clearly invalid. This covalence is shown to strongly affect the band structure, thermoelectric properties and response properties in the materials, with improved thermoelectric properties observed for those materials that least follow the Zintl concept. This expands our knowledge of the chemical bonding motifs governing physical properties, and gives a critical view on the simplistic chemical concepts too often applied for design of complex materials., Comment: 29 pages, 12 figures
- Published
- 2021
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26. Expression and interactions of stereo-chemically active lone pairs and their relation to structural distortions and thermal conductivity
- Author
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Tolborg, Kasper, Gatti, Carlo, and Iversen, Bo B.
- Subjects
Condensed Matter - Materials Science - Abstract
Stereo-chemically active lone pairs are typically described as an important non-bonding effect, and large interest has centered on understanding the derived effect of lone pair expression on physical properties such as the thermal conductivity. To manipulate such properties, it is essential to understand the conditions that lead to lone pair expression and to provide a quantitative chemical description. Here we first use density functional theory calculations to establish the presence of stereo-chemically active lone pairs on antimony in $\text{MnSb}_{2}\text{O}_{4}$. The lone pairs are formed through a similar mechanism to those in binary post-transition metal compounds in an oxidation state of two less than their main group number, where the degree of orbital interaction determines the expression of the lone pair. In $\text{MnSb}_{2}\text{O}_{4}$ the Sb lone pairs interact through a void space in the crystal structure, and they minimize their mutual repulsion by introducing a deflection angle. This angle increases significantly with decreasing Sb-Sb distance, thus showing the highly destabilizing nature of the lone pair interactions. Analysis of the chemical bonding in the structure shows that it is dominated by polar covalent interactions. A database search of related ternary chalcogenide structures shows that for structures with a lone pair the degree of lone pair expression is largely determined by whether the antimony-chalcogen units are connected or not, suggesting a cooperative effect. Isolated $\text{SbX}_3$ units have larger X-Sb-X bond angles, and therefore weaker lone pair expression than connected units. Since increased lone pair expression is equivalent to an increased orbital interaction (covalent bonding), which typically leads to increased heat conduction, this can explain the previously established correlation between larger bond angles and lower thermal conductivity., Comment: 30 pages (including supporting information), 8 figures
- Published
- 2020
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27. Multiscale Proper Orthogonal Decomposition (mPOD) of TR-PIV data-- a Case Study on Stationary and Transient Cylinder Wake Flows
- Author
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Mendez, Miguel A, Hess, David, Watz, Bo B, and Buchlin, Jean-Marie
- Subjects
Physics - Fluid Dynamics ,Mathematics - Dynamical Systems ,Physics - Instrumentation and Detectors - Abstract
Data-driven decompositions of Particle Image Velocimetry (PIV) measurements are widely used for a variety of purposes, including the detection of coherent features (e.g., vortical structures), filtering operations (e.g., outlier removal or random noise mitigation), data reduction and compression. This work presents the application of a novel decomposition method, referred to as Multiscale Proper Orthogonal Decomposition ( Mendez J Fluid Mech 870:988-1036, 2019) to Time-Resolved PIV (TR-PIV) measurement. This method combines Multiresolution Analysis (MRA) and standard Proper Orthogonal Decomposition (POD) to achieve a compromise between decomposition convergence and spectral purity of the resulting modes. The selected test case is the flow past a cylinder in both stationary and transient conditions, producing a frequency-varying Karman vortex street. The results of the mPOD are compared to the standard POD, the Discrete Fourier Transform (DFT) and the Dynamic Mode Decomposition (DMD). The mPOD is evaluated in terms of decomposition convergence and time-frequency localization of its modes. The multiscale modal analysis allows for revealing beat phenomena in the stationary cylinder wake, due to the three-dimensional nature of the flow, and to correctly identify the transition from various stationary regimes in the transient test case., Comment: Article submitted to Meas Sci Tech
- Published
- 2020
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28. Financial contribution as reason to opt out of non-invasive prenatal testing
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Bet, Bo B., Wielart, Lot, Ravelli, Anita C.J., van Wely, Madelon, van Leeuwen, Elisabeth, and Pajkrt, Eva
- Published
- 2023
- Full Text
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29. Factors related to fetal demise in cases with congenital heart defects
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Snoep, Maartje C., Bet, Bo B., Zwanenburg, Fleur, Knobbe, Ingmar, Linskens, Ingeborg H., Pajkrt, Eva, Rozendaal, Lieke, Van der Meeren, Lotte E., Clur, Sally-Ann, and Haak, Monique C.
- Published
- 2023
- Full Text
- View/download PDF
30. Solving the disordered structure of $\beta$-Cu$_{2-x}$Se using the three-dimensional difference pair distribution function
- Author
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Roth, Nikolaj and Iversen, Bo B.
- Subjects
Condensed Matter - Materials Science - Abstract
High-performing thermoelectric materials such as Zn$_4$Sb$_3$ and clathrates have atomic disorder as the root to their favorable properties. This makes it extremely difficult to understand and model their properties at a quantitative level, and thus effective structure-property relations are challenging to obtain. Cu$_{2-x}$Se is an intensely studied, cheap and non-toxic high performance thermoelectric, which exhibits highly peculiar transport properties, especially around the $\beta$ to $\alpha$ phase transition around 400 K, which must be related to the detailed nature of the crystal structure. Attempts to solve the crystal structure of the low temperature phase, $\beta$-Cu$_{2-x}$Se, have been unsuccessful since 1936. So far all studies have assumed that $\beta$-Cu$_{2-x}$Se has a three-dimensional periodic structure, but here we show that the structure is ordered only in two dimensions while being disordered in the third dimension with a highly disordered stacking sequence. Using the three-dimensional difference pair distribution function (3D-$\Delta$PDF) analysis method for diffuse single crystal X-ray scattering, we solve the structure of the ordered layer and show that there are two modes of stacking disorder present, which give rise to an average structure with higher symmetry. The present approach allows for a direct solution of structures with disorder in some dimensions and order in others. The local and extended structure of a solid determines its properties and Cu$_{2-x}$Se represents an example of a high-performing thermoelectric material where the local atomic structure differs significantly from the average periodic structure observed from Bragg crystallography.
- Published
- 2018
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31. Advanced thermoelectrics, What’s Next?
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Zhou, Jiali, primary, Zhang, Jiawei, additional, Iversen, Bo B., additional, and Shi, Xun, additional
- Published
- 2024
- Full Text
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32. Diagnostic accuracy of ultrasound screening for fetal structural abnormalities during the first and second trimester of pregnancy in low-risk and unselected populations
- Author
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Buijtendijk, Marieke FJ, additional, Bet, Bo B, additional, Leeflang, Mariska MG, additional, Shah, Harsha, additional, Reuvekamp, Tom, additional, Goring, Timothy, additional, Docter, Daniel, additional, Timmerman, Melanie GMM, additional, Dawood, Yousif, additional, Lugthart, Malou A, additional, Berends, Bente, additional, Limpens, Jacqueline, additional, Pajkrt, Eva, additional, van den Hoff, Maurice JB, additional, and de Bakker, Bernadette S, additional
- Published
- 2024
- Full Text
- View/download PDF
33. Nanoscale Surface Dynamics of Bi$_2$Te$_3$(111): Observation of a Prominent Surface Acoustic Wave and the Role of van der Waals Interactions
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Tamtögl, Anton, Campi, Davide, Bremholm, Martin, Hedegaard, Ellen M. J., Iversen, Bo B., Bianchi, Marco, Hofmann, Philip, Marzari, Nicola, Benedek, Giorgio, Ellis, John, and Allison, William
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We present a combined experimental and theoretical study of the surface vibrational modes of the topological insulator Bi$_2$Te$_3$. Using high-resolution helium-3 spin-echo spectroscopy we are able to resolve the acoustic phonon modes of Bi$_2$Te$_3$(111). The low energy region of the lattice vibrations is mainly dominated by the Rayleigh mode which has been claimed to be absent in previous experimental studies. The appearance of the Rayleigh mode is consistent with previous bulk lattice dynamics studies as well as theoretical predictions of the surface phonon modes. Density functional perturbation theory calculations including van der Waals corrections are in excellent agreement with the experimental data. Comparison of the experimental results with theoretically obtained values for films with a thickness of several layers further demonstrate, that for an accurate theoretical description of three-dimensional topological insulators with their layered structure the inclusion of van der Waals corrections is essential. The presence of a prominent surface acoustic wave and the contribution of van der Waals bonding to the lattice dynamics may hold important implications for the thermoelectric properties of thin-film and nanoscale devices.
- Published
- 2018
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34. A Helium-Surface Interaction Potential of Bi$_2$Te$_3$(111) from Ultrahigh-Resolution Spin-Echo Measurements
- Author
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Tamtögl, Anton, Pusterhofer, Michael, Bremholm, Martin, Hedegaard, Ellen M. J., Iversen, Bo B., Hofmann, Philip, Ellis, John, Allison, William, Miret-Artés, S., and Ernst, Wolfgang E.
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
We have determined an atom-surface interaction potential for the He$-$Bi$_2$Te$_3$(111) system by analysing ultrahigh resolution measurements of selective adsorption resonances. The experimental measurements were obtained using $^3$He spin-echo spectrometry. Following an initial free-particle model analysis, we use elastic close-coupling calculations to obtain a three-dimensional potential. The three-dimensional potential is then further refined based on the experimental data set, giving rise to an optimised potential which fully reproduces the experimental data. Based on this analysis, the He$-$Bi$_2$Te$_3$(111) interaction potential can be described by a corrugated Morse potential with a well depth $D=(6.22\pm0.05)~\mathrm{meV}$, a stiffness $\kappa =(0.92\pm0.01)~\mathrm{\AA}^{-1}$ and a surface electronic corrugation of $(9.6\pm0.2)$% of the lattice constant. The improved uncertainties of the atom-surface interaction potential should also enable the use in inelastic close-coupled calculations in order to eventually study the temperature dependence and the line width of selective adsorption resonances.
- Published
- 2018
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35. Electron-Phonon Coupling and Surface Debye Temperature of Bi$_2$Te$_3$(111) from Helium Atom Scattering
- Author
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Tamtögl, Anton, Kraus, Patrick, Avidor, Nadav, Bremholm, Martin, Hedegaard, Ellen M. J., Iversen, Bo B., Bianchi, Marco, Hofmann, Philip, Ellis, John, Allison, William, Benedek, Giorgio, and Ernst, Wolfgang E.
- Subjects
Condensed Matter - Materials Science - Abstract
We have studied the topological insulator Bi$_2$Te$_3$(111) by means of helium atom scattering. The average electron-phonon coupling $\lambda$ of Bi$_2$Te$_3$(111) is determined by adapting a recently developed quantum-theoretical derivation of the helium scattering probabilities to the case of degenerate semiconductors. Based on the Debye-Waller attenuation of the elastic diffraction peaks of Bi$_2$Te$_3$(111), measured at surface temperatures between $110~\mbox{K}$ and $355~\mbox{K}$, we find $\lambda$ to be in the range of $0.04-0.11$. This method allows to extract a correctly averaged $\lambda$ and to address the discrepancy between previous studies. The relatively modest value of $\lambda$ is not surprising even though some individual phonons may provide a larger electron-phonon interaction. Furthermore, the surface Debye temperature of Bi$_2$Te$_3$(111) is determined as ${\rm \Theta}_D = (81\pm6)~\mbox{K}$. The electronic surface corrugation was analysed based on close-coupling calculations. By using a corrugated Morse potential a peak-to-peak corrugation of 9% of the lattice constant is obtained., Comment: 9 pages, 4 figures
- Published
- 2017
- Full Text
- View/download PDF
36. Ubiquitous Presence and Novel Diversity of Anaerobic Alkane Degraders in Cold Marine Sediments.
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Gittel, Antje, Donhauser, Jonathan, Røy, Hans, Girguis, Peter R., Jørgensen, Bo B., and Kjeldsen, Kasper U.
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MARINE sediments ,GAS seepage ,COASTAL sediments ,HYDROTHERMAL vents ,OIL spills - Abstract
Alkanes are major constituents of crude oil and are released to the marine environment by natural seepage and from anthropogenic sources. Due to their chemical inertness, their removal from anoxic marine sediments is primarily controlled by the activity of anaerobic alkane-degrading microorganisms. To facilitate comprehensive cultivation-independent surveys of the diversity and distribution of anaerobic alkane degraders, we designed novel PCR primers that cover all known diversity of the 1-methylalkyl succinate synthase gene (masD/assA), which catalyzes the initial activation of alkanes. We studied masD/assA gene diversity in pristine and seepage-impacted Danish coastal sediments, as well as in sediments and alkane-degrading enrichment cultures from the Middle Valley (MV) hydrothermal vent system in the Pacific Northwest. MasD/assA genes were ubiquitously present, and the primers captured the diversity of both known and previously undiscovered masD/assA gene diversity. Seepage sediments were dominated by a single masD/assA gene cluster, which is presumably indicative of a substrate-adapted community, while pristine sediments harbored a diverse range of masD/assA phylotypes including those present in seepage sediments. This rare biosphere of anaerobic alkane degraders will likely increase in abundance in the event of seepage or accidental oil spillage. Nanomolar concentrations of short-chain alkanes (SCA) were detected in pristine and seepage sediments. Interestingly, anaerobic alkane degraders closely related to strain BuS5, the only SCA degrader in pure culture, were found in mesophilic MV enrichments, but not in cold sediments from Danish waters. We propose that the new masD/assA gene lineages in these sediments represent novel phylotypes that are either fueled by naturally occurring low levels of SCA or that metabolize medium- to long-chain alkanes. Our study highlights that masD/assA genes are a relevant diagnostic marker to identify seepage and microseepage, e.g., during prospecting for oil and gas, and may act as an indicator of anthropogenic oil spills in marine sediments. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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- View/download PDF
37. Continuous-Flow Synthesis of Zn1–xMnxS Nanoparticles at Ambient Conditions.
- Author
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Borup, Anders B., Bjerre-Christensen, Nanna, Bertelsen, Andreas D., Mamakhel, Aref H., Bondesgaard, Martin, and Iversen, Bo B.
- Published
- 2024
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38. H2S‑Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions.
- Author
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Olesen, Soffi E.S., Jensen, Anders W., Kløve, Magnus, Fenini, Filippo, Nissen, Jesper, Iversen, Bo B., Bentien, Anders, and Nielsen, Lars P.
- Published
- 2024
- Full Text
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39. Abstract WP92: Application of a Horizontal Communication Process in Combination With Artificial Intelligence (AI) to Improve Stroke Care in Patients With Large Vessel Occlusion (LVO)
- Author
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Kashyap, Bhavani, primary, Herrmann, Amanda A, additional, Droegemueller, Carol J, additional, Gustafson, Sally K, additional, Malek, Abigail M, additional, Nyamao, Tiffan M, additional, Seth, Srishti, additional, Sathe, Mihika M, additional, Isberg, Anna E, additional, Hatton, Sarah J, additional, Podgorski, Bo B, additional, and Sabayan, Behnam, additional
- Published
- 2024
- Full Text
- View/download PDF
40. Continuous-Flow Synthesis of Zn1–xMnxS Nanoparticles at Ambient Conditions
- Author
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Borup, Anders B., Bjerre-Christensen, Nanna, Bertelsen, Andreas D., Mamakhel, Aref H., Bondesgaard, Martin, and Iversen, Bo B.
- Abstract
With its large direct band gap and good chemical stability, ZnS is suitable for many applications, including light-emitting diodes, panel displays, and photodetection. Here, nanoparticles of ZnS are synthesized phase pure under ambient conditions by precipitation in a simple and scalable continuous-flow reactor. Furthermore, different degrees of Zn substitution with Mn have been investigated, Zn1–xMnxS, with x= 0.05, 0.19, and 0.25 according to X-ray fluorescence measurements. The products are analyzed with multitemperature synchrotron powder X-ray diffraction (PXRD) and X-ray total scattering. The analysis reveals phase-pure synthesis products with the sphalerite structure and crystallite sizes in the range of 3.8–4.7 nm in agreement with scanning transmission electron microscopy. Only Zn0.75Mn0.25S shows traces of Mn3O4, indicating that x= 0.25 is above the substitution limit as the impurity appears. Substitution of Zn with Mn in the nanoparticles is confirmed by energy-dispersive X-ray spectroscopy, as well as an observed decrease in the band gap, decrease in the sphalerite-to-wurtzite phase transition temperature, and increase in the unit cell dimensions with increasing Mn content. Based on the modeling of the PXRD Rietveld refined atomic displacement parameters, the Debye temperature for ZnS and Zn0.95Mn0.05S is determined to be 322 ± 13 and 394 ± 22 K, respectively.
- Published
- 2024
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41. Large Seebeck Effect by Charge-Mobility Engineering
- Author
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Sun, Peijie, Wei, Beipei, Zhang, Jiahao, Tomczak, Jan M., Strydom, A. M., Søndergaard, M., Iversen, Bo B., and Steglich, Frank
- Subjects
Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The Seebeck effect describes the generation of an electric potential in a conducting solid exposed to a temperature gradient. Besides fundamental relevance in solid state physics, it serves as a key quantity to determine the performance of functional thermoelectric materials. In most cases, it is dominated by an energy-dependent electronic density of states at the Fermi level, in line with the prevalent efforts toward superior thermoelectrics through the engineering of electronic structure. Here, we demonstrate an alternative source for the Seebeck effect based on charge-carrier relaxation: A charge mobility that changes rapidly with temperature can result in a sizeable addition to the Seebeck coefficient. This new Seebeck source is demonstrated explicitly for Ni-doped CoSb3, where a dramatic mobility change occurs due to the crossover between two different charge-relaxation regimes. Our findings unveil the origin of pronounced features in the Seebeck coefficient of many other elusive materials characterized by a significant mobility mismatch. As the physical origin for the latter can vary greatly, our proposal provides a unifying framework for the understanding of a large panoply of thermoelectric phenomena. When utilized appropriately, this effect can also provide a novel route to the design of improved thermoelectric materials for applications in solid-state cooling or power generation., Comment: 12 pages, 4 figures and 1 table
- Published
- 2015
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42. Crystal Structure, Electronic Transport, and Improved Thermoelectric Properties of Doped InTe.
- Author
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Song, Lirong, Zhang, Jiawei, Mamakhel, Aref, and Iversen, Bo B.
- Published
- 2024
- Full Text
- View/download PDF
43. Increased Pulmonary-Aortic Interspace in Fetal Right Aortic Arch: A Matched Case-Control Study.
- Author
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Bet, Bo B., van Steijn, Agnes E., Linskens, Ingeborg H., Knobbe, Ingmar, van Leeuwen, Elisabeth, Pajkrt, Eva, and Clur, Sally-Ann
- Subjects
- *
THORACIC aorta , *VENA cava superior , *CASE-control method , *PULMONARY artery , *SUPERIOR vena cava syndrome , *RECEIVER operating characteristic curves - Abstract
Introduction: The prenatal detection rate of a right aortic arch (RAA) has increased with the implementation of the three-vessel view (3VV) to the second-trimester anomaly scan formed by the pulmonary artery (PA), aorta (Ao), and superior vena cava (SVC). We examined the value of measuring the distance between PA and Ao in the 3VV in cases with an RAA. Methods: We conducted a case-control study in which fetuses with an isolated RAA were matched to 3 healthy controls. Using 3VV images, the distances between PA, Ao, and SVC were measured and the ratio between PA to Ao (PAAo) distance and Ao to SVC (AoSVC) distance was calculated. Results: Fifty-four RAA cases and 162 matched controls were included. The mean absolute distance PAAo was 3.1 mm in cases and 1.8 mm in controls (p < 0.001), and the mean PAAo/AoSVC ratio was 2.9 and 1.4, respectively (p < 0.001). The ROC curve of PAAo/AoSVC ratio showed a cut-off point of 1.9 with sensitivity and specificity over 87% for the diagnosis of RAA. Conclusions: The pulmonary-aortic interspace and the PAAo/AoSVC ratio were significantly larger for RAA cases as compared to controls. If an increased pulmonary-aortic interspace is observed, a PAAo/AoSVC of ≥1.9 can be helpful in the diagnosis of an RAA. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. Phylogeny and physiology of candidate phylum ‘Atribacteria’ (OP9/JS1) inferred from cultivation-independent genomics
- Author
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Nobu, Masaru K, Dodsworth, Jeremy A, Murugapiran, Senthil K, Rinke, Christian, Gies, Esther A, Webster, Gordon, Schwientek, Patrick, Kille, Peter, Parkes, R John, Sass, Henrik, Jørgensen, Bo B, Weightman, Andrew J, Liu, Wen-Tso, Hallam, Steven J, Tsiamis, George, Woyke, Tanja, and Hedlund, Brian P
- Subjects
Microbiology ,Biological Sciences ,Ecology ,Genetics ,Human Genome ,Bacteria ,Genomics ,Geologic Sediments ,Lakes ,Molecular Sequence Data ,Phylogeny ,Environmental Sciences ,Technology ,Biological sciences ,Environmental sciences - Abstract
The 'Atribacteria' is a candidate phylum in the Bacteria recently proposed to include members of the OP9 and JS1 lineages. OP9 and JS1 are globally distributed, and in some cases abundant, in anaerobic marine sediments, geothermal environments, anaerobic digesters and reactors and petroleum reservoirs. However, the monophyly of OP9 and JS1 has been questioned and their physiology and ecology remain largely enigmatic due to a lack of cultivated representatives. Here cultivation-independent genomic approaches were used to provide a first comprehensive view of the phylogeny, conserved genomic features and metabolic potential of members of this ubiquitous candidate phylum. Previously available and heretofore unpublished OP9 and JS1 single-cell genomic data sets were used as recruitment platforms for the reconstruction of atribacterial metagenome bins from a terephthalate-degrading reactor biofilm and from the monimolimnion of meromictic Sakinaw Lake. The single-cell genomes and metagenome bins together comprise six species- to genus-level groups that represent most major lineages within OP9 and JS1. Phylogenomic analyses of these combined data sets confirmed the monophyly of the 'Atribacteria' inclusive of OP9 and JS1. Additional conserved features within the 'Atribacteria' were identified, including a gene cluster encoding putative bacterial microcompartments that may be involved in aldehyde and sugar metabolism, energy conservation and carbon storage. Comparative analysis of the metabolic potential inferred from these data sets revealed that members of the 'Atribacteria' are likely to be heterotrophic anaerobes that lack respiratory capacity, with some lineages predicted to specialize in either primary fermentation of carbohydrates or secondary fermentation of organic acids, such as propionate.
- Published
- 2016
45. Intra- and Interband Electron Scattering in the Complex Hybrid Topological Insulator Bismuth Bilayer on Bi$_2$Se$_3$
- Author
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Eich, A., Michiardi, M., Bihlmayer, G., Zhu, X. -G., Mi, J. -L., Iversen, Bo B., Wiesendanger, R., Hofmann, Ph., Khajetoorians, A. A., and Wiebe, J.
- Subjects
Condensed Matter - Mesoscale and Nanoscale Physics - Abstract
The band structure, intra- and interband scattering processes of the electrons at the surface of a bismuth-bilayer on Bi$_2$Se$_3$ have been experimentally investigated by low-temperature Fourier-transform scanning tunneling spectroscopy. The observed complex quasiparticle interference patterns are compared to a simulation based on the spin-dependent joint density of states approach using the surface-localized spectral function calculated from first principles as the only input. Thereby, the origin of the quasiparticle interferences can be traced back to intraband scattering in the bismuth bilayer valence band and Bi$_2$Se$_3$ conduction band, and to interband scattering between the two-dimensional topological state and the bismuth-bilayer valence band. The investigation reveals that the bilayer band gap, which is predicted to host one-dimensional topological states at the edges of the bilayer, is pushed several hundred milli-electronvolts above the Fermi level. This result is rationalized by an electron transfer from the bilayer to Bi$_2$Se$_3$ which also leads to a two-dimensional electron state in the Bi$_2$Se$_3$ conduction band with a strong Rashba spin-splitting, coexisting with the topological state and bilayer valence band., Comment: 11 pages, 5 figures
- Published
- 2014
- Full Text
- View/download PDF
46. Direct observation of one-dimensional disordered diffusion channel in a chain-like thermoelectric with ultralow thermal conductivity
- Author
-
Zhang, Jiawei, Roth, Nikolaj, Tolborg, Kasper, Takahashi, Seiya, Song, Lirong, Bondesgaard, Martin, Nishibori, Eiji, and Iversen, Bo B.
- Published
- 2021
- Full Text
- View/download PDF
47. Creating a Typology of International Alliances with City-level Distance Measures
- Author
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Engsig, Juliane, primary, Nielsen, Bo B., additional, Chiambaretto, Paul, additional, and Ramaroson, Andry, additional
- Published
- 2021
- Full Text
- View/download PDF
48. Highly Dispersive Electron Relaxation and Colossal Thermoelectricity in the Correlated Semiconductor FeSb$_2$
- Author
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Sun, Peijie, Xu, Wenhu, Tomczak, Jan M., Kotliar, Gabriel, Sondergaard, Martin, Iversen, Bo B., and Steglich, Frank
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
We show that the colossal thermoelectric power, $S(T)$, observed in the correlated semiconductor FeSb$_2$ below 30\,K is accompanied by a huge Nernst coefficient $\nu(T)$ and magnetoresistance MR$(T)$. Markedly, the latter two quantities are enhanced in a strikingly similar manner. While in the same temperature range, $S(T)$ of the reference compound FeAs$_2$, which has a seven-times larger energy gap, amounts to nearly half of that of FeSb$_2$, its $\nu(T)$ and MR$(T)$ are intrinsically different to FeSb$_2$: they are smaller by two orders of magnitude and have no common features. With the charge transport of FeAs$_2$ successfully captured by the density functional theory, we emphasize a significantly dispersive electron-relaxation time $\tau(\epsilon_k)$ due to electron-electron correlations to be at the heart of the peculiar thermoelectricity and magnetoresistance of FeSb$_2$., Comment: 8 pages, 5 figures
- Published
- 2013
- Full Text
- View/download PDF
49. Formation Mechanism and Excitonic Luminescence of Supercritical-Fluid-Synthesized ZnO Nanoparticles
- Author
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Brian Dusolle, Véronique Jubera, Evgeniy S. Ilin, Patrick Martin, Gilles Philippot, Matthew R. Suchomel, Bo B. Iversen, Samuel Marre, Cyril Aymonier, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Université de Bordeaux (UB)-Institut Polytechnique de Bordeaux-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Centre d'Etudes Lasers Intenses et Applications (CELIA), Université de Bordeaux (UB)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Centre National de la Recherche Scientifique (CNRS), Center for Integrated Materials Research, Aarhus University [Aarhus], Interdisciplinary Nanoscience Center (iNANO), The CNRS and the Nouvelle Aquitaine region. This study was performed with financial support from the French State, managed by the French National Research Agency (ANR) in the frame of a nonthematic program (ANR-2010-BLANC-0820) and in the frame of 'the Investments for the future' Program IDEX Bordeaux - LAPHIA (ANR-10-IDEX-03-02). The Villum Foundation is thanked for support. We gratefully acknowledge DESY (Hamburg, Germany), a member of the Helmholz Association HGF, for granting beamtime at PETRA-III. The LIGHT S&T Graduate Program (PIA3 Investment for the Future Program, ANR-17-EURE-0027)., ANR-10-IDEX-0302,ANR-10-IDEX-03-02,Investments for the Future Programme IdEx Bordeaux-LAPHIA, and ANR-17-EURE-0027,LIGHTS&T,University of Bordeaux Graduate Scholl in Light Sciences & Technologies(2017)
- Subjects
Metal oxide nanoparticles ,Crystal structure ,General Chemical Engineering ,Materials Chemistry ,Nanoparticles ,Excitons ,Oxides ,[CHIM.MATE]Chemical Sciences/Material chemistry ,General Chemistry - Abstract
International audience; Extensive research on nanosized ZnO has proven that its optical properties are challenging to control due to a number of possible defects producing various emissions in the visible range. Our group proposed a low-temperature, supercritical-fluid-driven synthesis of isotropic nanosized particles that exhibit a unique and unprecedentedly pure excitonic emission, comparable to that of single crystals. The present article reports the growth mechanism at the origin of the unexpectedly pure excitonic emission as well as a more detailed study of its optical properties at liquid helium temperatures. The ZnO phase is obtained via the thermal decomposition of an intermediate ZnO2 phase. No bulk defect luminescence is detected, and the synthesis route leaves a “ZnO2-like” surface able to neutralize the formation of surface defects, which can contribute to visible emissions. The luminescence measurements were performed at liquid helium temperature to enable the identification of excitons. The investigation of the photoluminescence properties confirms a strong excitonic emission in the UV region with no visible band and sheds light on a phonon coupling with the E2 high vibrational mode.
- Published
- 2023
50. Enhanced electron correlations in FeSb$_2$
- Author
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Sun, Peijie, Søndergaard, Martin, Iversen, Bo B., and Steglich, Frank
- Subjects
Condensed Matter - Strongly Correlated Electrons - Abstract
FeSb$_2$ has been recently identified as a new model system for studying many-body renormalizations in a $d$-electron based narrow gap semiconducting system, strongly resembling FeSi. The electron-electron correlations in FeSb$_2$ manifest themselves in a wide variety of physical properties including electrical and thermal transport, optical conductivity, magnetic susceptibility, specific heat and so on. We review some of the properties that form a set of experimental evidences revealing the crucial role of correlation effects in FeSb$_2$. The metallic state derived from slight Te doping in FeSb$_2$, which has large quasiparticle mass, will also be introduced., Comment: 9 pages, 7 figures; submitted to Annalen der Physik
- Published
- 2011
- Full Text
- View/download PDF
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