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2. Surface adatom conductance filtering in scanning tunneling spectroscopy of Co-doped BaFe2As2 iron pnictide superconductors

Author

Koepernik, K., Johnston, S., van Heumen, E., Huang, Y., Kaas, J., Goedkoop, J. B., Golden, M. S., and Brink, Jeroen van den

Subjects
Condensed Matter - Superconductivity
Abstract

We establish in a combination of ab initio theory and experiments that the tunneling process in scanning tunneling microscopy/spectroscopy on the A-122 iron pnictide superconductors - in this case BaFe$_{2-x}$Co$_x$As$_2$ - involve a strong adatom filtering of the differential conductance from the near-EF Fe3d states, which in turn originates from the top-most sub-surface Fe layer of the crystal. The calculations show that the dominance of surface Ba-related tunneling pathways leaves fingerprints found in the experimental differential conductance data, including large particle-hole asymmetry and an energy-dependent contrast inversion., Comment: 4.5 pages, 4 figures. To appear in Physical Review Letters

Published
2012
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3. Multiband quasiparticle interference in the topological insulator Cu_(x)Bi_(2)Te_(3)

Author

van Heumen, E., van Dalum, G. A. R., Kaas, J., de Jong, N., Oen, J., Huang, Y. K., Mitchell, A. K., Fritz, L., and Golden, M. S.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Strongly Correlated Electrons
Abstract

We present angle resolved photoemission experiments and scanning tunneling spectroscopy results on the doped topological insulator Cu0.2Bi2Te3. Quasi-particle interference (QPI) measurements, based on high resolution conductance maps of the local density of states show that there are three distinct energy windows for quasi-particle scattering. Using a model Hamiltonian for this system two new scattering channels are identified: the first between the surface states and the conduction band and the second between conduction band states. We also observe that the real space density modulation has a predominant three-fold symmetry, which rules out a simple, isotropic impurity potential. We obtain agreement between experiment and theory by considering a modified scattering potential that is consistent with having mostly Bi-Te anti-site defects as scatterers., Comment: Updated the discussion of results. New model for impurity scattering added to the discussion. Corrected labelling of some figures

Published
2011

4. Pseudogap-less high T$_{c}$ superconductivity in BaCo$_{x}$Fe$_{2-x}$As$_{2}$

Author

Massee, F., Huang, Y. K., Kaas, J., van Heumen, E., de Jong, S., Huisman, R., Luigjes, H., Goedkoop, J. B., and Golden, M. S.

Subjects
Condensed Matter - Superconductivity
Abstract

The pseudogap state is one of the peculiarities of the cuprate high temperature superconductors. Here we investigate its presence in BaCo$_{x}$Fe$_{2-x}$As$_{2}$, a member of the pnictide family, with temperature dependent scanning tunneling spectroscopy. We observe that for under, optimally and overdoped systems the gap in the tunneling spectra always closes at the bulk T$_{c}$, ruling out the presence of a pseudogap state. For the underdoped case we observe superconducting gaps over large fields of view, setting a lower limit of tens of nanometers on the length scale of possible phase separated regions., Comment: 5 pages, 3 figures

Published
2010
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5. Dissimilarities between the electronic structure of chemically doped and chemically pressurized iron pnictides from an angle-resolved photoemission spectroscopy study

Author

Thirupathaiah, S., Rienks, E. D. L., Jeevan, H. S., Ovsyannikov, R., Slooten, E., Kaas, J., van Heumen, E., de Jong, S., Duerr, H. A., Siemensmeyer, K., Follath, R., Gegenwart, P., Golden, M. S., and Fink, J.

Subjects
Condensed Matter - Superconductivity
Abstract

We have studied the electronic structure of EuFe2As2-xPx using high resolution angle-resolved photoemission spectroscopy. Upon substituting As with the isovalent P, which leads to a chemical pressure and to superconductivity, we observe a non-rigid-band like change of the electronic structure along the center of the Brillouin zone (BZ): an orbital and kz dependent increase or decrease in the size of the hole pockets near the Gamma - Z line. On the other hand, the diameter of the Fermi surface cylinders at the BZ corner forming electron pockets, hardly changes. This is in stark contrast to p and n-type doped iron pnictides where, on the basis of ARPES experiments, a more rigid-band like behavior has been proposed. These findings indicate that there are different ways in which the nesting conditions can be reduced causing the destabilization of the antiferromagnetic order and the appearance of the superconducting dome., Comment: 5 pages, 3 figures

Published
2010
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6. The cleavage surface of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) superconductors: from diversity to simplicity

Author

Massee, F., de Jong, S., Huang, Y., Kaas, J., van Heumen, E., Goedkoop, J. B., and Golden, M. S.

Subjects
Condensed Matter - Superconductivity
Abstract

We elucidate the termination surface of cleaved single crystals of the BaFe_(2-x)Co_(x)As_(2) and Fe_(y)Se_(1-x)Te_(x) families of the high temperature iron based superconductors. By combining scanning tunneling microscopic data with low energy electron diffraction we prove that the termination layer of the Ba122 systems is a remnant of the Ba layer, which exhibits a complex diversity of ordered and disordered structures. The observed surface topographies and their accompanying superstructure reflections in electron diffraction depend on the cleavage temperature. In stark contrast, Fe_(y)Se_(1-x)Te_(x) possesses only a single termination structure - that of the tetragonally ordered Se_(1-x)Te_(x) layer., Comment: 4 pages, 4 figures

Published
2009
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9. Estimation of diarrhoeal infection risk in parks and recreational areas after urban flooding

Author

Jørgensen, C., Mark, O., Albrechtsen, Hans-Jørgen, Jørgensen, M. E., Schultz, Anna Charlotte, Petersen, Heidi Huus, Clauson-Kaas, J., Jørgensen, C., Mark, O., Albrechtsen, Hans-Jørgen, Jørgensen, M. E., Schultz, Anna Charlotte, Petersen, Heidi Huus, and Clauson-Kaas, J.

Abstract

Urban cloudburst management may include intentional temporary storage of flood water in parks or other recreational areas. In cities with combined sewers this will expose the population to wastewater and increase the risk of diarrhoeal disease. We present an approach to estimate the risk of diarrhoeal disease after urban flooding of a green area by combining hydraulic modelling, an experimental flood simulation and quantitative microbial risk assessment (QMRA). The method allows the cloudburst manager to reduce unacceptable disease risks during the planning of cloudburst management or on existing facilities.

Published
2021

12. Plasticity — Memory — Attention

Author

Vidyasagar, T. R., primary, Gilbert, C. D., additional, Wiesel, T. N., additional, Kaas, J. H., additional, Florence, S. L., additional, Scheich, H., additional, Simonis, C., additional, Ohl, F., additional, Thomas, H., additional, Tillein, J., additional, Goldberg, M. E., additional, Musil, S. Y., additional, Colby, C. L., additional, Duhamel, J.-R., additional, Olson, C. R., additional, Desimone, R., additional, Chelazzi, L., additional, Miller, E., additional, and Duncan, J., additional

Published
1994
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19. Auditing local methods for quality assurance in radiotherapy using the same set of predefined treatment plans

Author

Seravalli, E., Houweling, A.C. (Arjan), Van Battum, L., Raaben, T.A., Kuik, M., Pooter, J.A. (Jacobus Abraham) de, Van Gellekom, M.P.R., Kaas, J., de Vries, W., Loeff, E.A., Van de Kamer, J.B., Seravalli, E., Houweling, A.C. (Arjan), Van Battum, L., Raaben, T.A., Kuik, M., Pooter, J.A. (Jacobus Abraham) de, Van Gellekom, M.P.R., Kaas, J., de Vries, W., Loeff, E.A., and Van de Kamer, J.B.

Abstract

Background and purpose: Local implementation of plan-specific quality assurance (QA) methods for intensitymodulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) treatment plans may vary because of dissimilarities in procedures, equipment and software. The purpose of this work is detecting possible differences between local QA findings and those of an audit, using the same set of treatment plans. Methods: A pre-defined set of clinical plans was devised and imported in the participating institute’s treatment planning system for dose computation. The dose distribution was measured using an ionisation chamber, radiochromic film and an ionisation chamber array. The centres performed their own QA, which was compared to the audit findings. The agreement/disagreement between the audit and the institute QA results were assessed along with the differences between the dose distributions measured by the audit team and computed by the institute. Results: For the majority of the cases the results of the audit were in agreement with the institute QA findings: ionisation chamber: 92%, array: 88%, film: 76% of the total measurements. In only a few of these cases the evaluated measurements failed for both: ionisation chamber: 2%, array: 4%, film: 0% of the total measurements. Conclusion: Using predefined treatment plans, we found that in approximately 80% of the evaluated measurements the results of local QA of IMRT and VMAT plans were in line with the findings of the audit. However, the percentage of agreement/disagreement depend

Published
2018
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22. Copenhagen: Rainwater quality and handling of urban run-off

Author

Clauson-Kaas, J., Mose Poulsen, B., Skov, J., Dam Joensen, S., and Brelot, Elodie

Subjects
climat, [SDE.IE]Environmental Sciences/Environmental Engineering, aide à la décision, decision aid, approche globale, global approach
Abstract

Colloque avec actes et comité de lecture. Internationale.; International audience

Published
2016

26. Multi-institutional dosimetric and geometric commissioning of image-guided small animal irradiators

Author

Lindsay, P. E., Granton, P. V., Gasparini, Alessia, Jelveh, S., Clarkson, R., van Hoof, S., Hermans, J., Kaas, J., Wittkamper, F., Sonke, J. -J., Verhaegen, F., Jaffray, D. A., Promovendi ODB, Promovendi PHPC, Huisartsgeneeskunde, Radiotherapie, RS: GROW - Oncology, and RS: GROW - R3 - Innovative Cancer Diagnostics & Therapy

Subjects
Computer. Automation, pre-clinical, image-guidance, small animal irradiation, kV dosimetry
Abstract

Purpose: To compare the dosimetric and geometric properties of a commercial x-ray based image-guided small animal irradiation system, installed at three institutions and to establish a complete and broadly accessible commissioning procedure. Methods: The system consists of a 225 kVp x-ray tube with fixed field size collimators ranging from 1 to 44 mm equivalent diameter. The x-ray tube is mounted opposite a flat-panel imaging detector, on a C-arm gantry with 360. coplanar rotation. Each institution performed a full commissioning of their system, including half-value layer, absolute dosimetry, relative dosimetry (profiles, percent depth dose, and relative output factors), and characterization of the system geometry and mechanical flex of the x-ray tube and detector. Dosimetric measurements were made using Farmer-type ionization chambers, small volume air and liquid ionization chambers, and radiochromic film. The results between the three institutions were compared. Results: At 225 kVp, with 0.3 mm Cu added filtration, the first half value layer ranged from 0.9 to 1.0 mm Cu. The dose-rate in-air for a 40 x 40 mm(2) field size, at a source-to-axis distance of 30 cm, ranged from 3.5 to 3.9 Gy/min between the three institutions. For field sizes between 2.5 mm diameter and 40 x 40 mm2, the differences between percent depth dose curves up to depths of 3.5 cm were between 1% and 4% on average, with the maximum difference being 7%. The profiles agreed very well for fields >5 mm diameter. The relative output factors differed by up to 6% for fields larger than 10 mm diameter, but differed by up to 49% for fields

Published
2014

27. The Monotreme Nervous System

Author

Kaas, J, Ashwell, KW, Kaas, J, and Ashwell, KW

Abstract

All biology only makes sense when seen in the light of evolution, and this is especially true for the nervous system.

Published
2016

31. Approche adaptative holistique dans le square Sct Annae à Copenhague

Author

Nyerup Nielsen, C., Slot Hansen, S., Lindholm Krak, A., Andersen, S.M., Clausson-Kaas, J., Bach, O., RAMBOLL, and Brelot, Elodie

Subjects
Stratégie, Récupération des eaux pluviales, [SDE.IE]Environmental Sciences/Environmental Engineering, Urban design, Strategy, Aménagement, Stormwater harvesting
Abstract

Colloque avec actes et comité de lecture. Internationale.; International audience

Published
2013

34. EP-1560: A national QA audit for IMRT and VMAT

Author

Seravalli, E., primary, Houweling, A.C., additional, Van Gellekom, M.P.R., additional, Kaas, J., additional, Kuik, M., additional, Loeff, E., additional, Raaben, T.A., additional, De Pooter, J.A., additional, De Vries, J.H.W., additional, and Van de Kamer, J.B., additional

Published
2015
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35. Cleavage surfaces of the BaFe2−xCoxAs2 and FeySe1−xTex superconductors: A combined STM plus LEED study

Author

Massee, F., de Jong, S., Huang, Y., Kaas, J., van Heumen, E., Goedkoop, J.B., Golden, M.S., and Hard Condensed Matter (WZI, IoP, FNWI)

Abstract

We elucidate the termination surface of cleaved single crystals of the BaFe2−xCoxAs2 and FeySe1−xTex families of the high-temperature iron-based superconductors. By combining scanning tunneling microscopic data with low-energy electron diffraction we prove that the termination layer of the BaFe2As2 systems is a remnant of the Ba layer, which exhibits a complex diversity of ordered and disordered structures. The observed surface topographies and their accompanying superstructure reflections in electron diffraction depend on the cleavage temperature. In stark contrast, FeySe1−xTex possesses only a single termination structure—that of the tetragonally ordered Se1−xTex layer.

Published
2009

38. Life cycle assessment of three water systems in Copenhagen-a management tool of the future.

Author

Godskesen, Berit, Zambrano, K C, Trautner, A., Johansen, N-B., Thiesson, L., Andersen, L., Clauson-Kaas, J., Neidel, T. L., Rygaard, Martin, Kløverpris, N. H., Albrechtsen, Hans-Jørgen, Godskesen, Berit, Zambrano, K C, Trautner, A., Johansen, N-B., Thiesson, L., Andersen, L., Clauson-Kaas, J., Neidel, T. L., Rygaard, Martin, Kløverpris, N. H., and Albrechtsen, Hans-Jørgen

Abstract

Environmental life-cycle assessment (LCA) was applied to evaluate three different water systems of the water sector in Copenhagen, Denmark, including technologies within water supply, facilities recycling water and treatment of sewer overflow. In these three water systems LCA was used to evaluate the environmental impacts of each of the processes involved. The overall conclusion was that LCA is suitable as a decision support tool in the water sector as it provides a holistic evaluation platform of the considered alternatives categorised in environmental impact categories. The use of LCA in the water sector of this region has limitations since it does not yet consider impact categories assessing freshwater scarcity and ecological sustainability.

Published
2011

42. Neuroscience - Rewiring the adult brain

Author

Calford, Mike, Chino, Y, Das, A, Eysel, U, Gilbert, C, Heinen, S, Kaas, J, Ullman, S, Calford, Mike, Chino, Y, Das, A, Eysel, U, Gilbert, C, Heinen, S, Kaas, J, and Ullman, S

Abstract

Arising from: S. M. Smirnakis et al. Nature 435, 300-307 (2005)

Published
2005

49. Dissimilarities between the electronic structure of chemically doped and chemically pressurized iron pnictides from an angle-resolved photoemission spectroscopy study

Author

Thirupathaiah, S., primary, Rienks, E. D. L., additional, Jeevan, H. S., additional, Ovsyannikov, R., additional, Slooten, E., additional, Kaas, J., additional, van Heumen, E., additional, de Jong, S., additional, Dürr, H. A., additional, Siemensmeyer, K., additional, Follath, R., additional, Gegenwart, P., additional, Golden, M. S., additional, and Fink, J., additional

Published
2011
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