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134 results on '"Matthiesen J."'

2. A search for solar-like oscillations in K giants in the globular cluster M4

Author

Frandsen, S., Bruntt, H., Grundahl, F., Kopacki, G., Kjeldsen, H., Arentoft, T., Stello, D., Bedding, T. R., Jacob, A. P., Gilliland, R. L., Edmonds, P. D., Michel, E., and Matthiesen, J.

Subjects
Astrophysics
Abstract

To expand the range in the colour-magnitude diagram where asteroseismology can be applied, we organized a photometry campaign to find evidence for solar-like oscillations in giant stars in the globular cluster M4. The aim was to detect the comb-like p-mode structure characteristic for solar-like oscillations in the amplitude spectra. The two dozen main target stars are in the region of the bump stars and have luminosities in the range 50-140 Lsun. We collected 6160 CCD frames and light curves for about 14000 stars were extracted. We obtain high quality light curves for the K giants, but no clear oscillation signal is detected. High precision differential photometry is possible even in very crowded regions like the core of M4. Solar-like oscillations are probably present in K giants, but the amplitudes are lower than classical scaling laws predict., Comment: 14 pages, 16 figures, accepted for publication in A&A

Published
2007
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3. The effects of relocation on Royal Air Force families

Author

Matthiesen, J. K.

Subjects
358.4, Business and Administrative studies
Abstract

This doctoral research project examines the effects that geographical transience has on Royal Air Force families. The methodology employed in this exploratory and qualitative study consisted largely of open-ended interview questions but also included a series of demographic variables. In total, 29 RAF personnel without families, 33 RAF personnel with families, 33 RAF spouses, and 15 RAF children participated in this research (N = 110). All respondents volunteered to take part in the study and were based in the United Kingdom at the time of data collection. The interviews were transcribed and content coded according to six major relocation themes arising from the literature (change, tasks, support, coping, difficulty, and outcome). QSR NVIVO 2.0, a qualitative data analysis software package, was used to facilitate the process. Through the utilisations of qualitative methodology, the researcher was able to offer various novel and reoccurring variables that appear to play an important role (at least subjectively) in relocation. Additionally, frequencies associated with these factors were presented. The findings were integrated with those from the literature in order to offer an initial comparison and differentiation between civilian and military samples. The main theoretical contributions were the introduction of the concept of mobile mentality, the creation of a novel relocation model that takes familial interaction into account, and the development of a taxonomy for the classification of relocation outcomes. Finally, additional observations, recommendations for future research, and practical implications are reviewed.

Published
2005
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6. First-Principles Prediction of Surface Wetting

Author

Andersson, M. P., Hassenkam, T., Matthiesen, J., Nikolajsen, L., Okhrimenko, D., Dobberschuetz, S., Stipp, S. L. S., Andersson, M. P., Hassenkam, T., Matthiesen, J., Nikolajsen, L., Okhrimenko, D., Dobberschuetz, S., and Stipp, S. L. S.

Abstract

We have developed a method for predicting the solvation contribution to solid-liquid interfacial tension (IFT) based on density functional theory and the implicit solvent model COSMO-RS. Our method can be used to predict wetting behavior for a solid surface in contact with two liquids. We benchmarked our method against measurements of contact angle from water-inoil on silica wafers and a range of self-assembled monolayers (SAMs) with different compositions, ranging from oil-wet to water-wet. We also compared our predictions to literature data for wetting of a polydimethylsilane surface. By explicitly including deprotonation for silica surfaces and carboxylic acid SAMs, very good agreement was obtained with experimental data for nearly all surfaces. Poor agreement was found for amine-terminated SAMs, which could be the result of both method and model insufficiencies and impurities known to be present for such surfaces. Solid-liquid IFT cannot be measured directly, making predictions such as from our method all the more important.

Published
2020

16. Controlling biomineralisation with cations

Author

Sand, K. K., Pedersen, C. S., Matthiesen, J., Dobberschutz, S., Stipp, S. L. S., Sand, K. K., Pedersen, C. S., Matthiesen, J., Dobberschutz, S., and Stipp, S. L. S.

Published
2017

18. Minimal methylation classifier (MIMIC): A novel method for derivation and rapid diagnostic detection of disease-associated DNA methylation signatures

Author

Schwalbe, E. C., primary, Hicks, D., additional, Rafiee, G., additional, Bashton, M., additional, Gohlke, H., additional, Enshaei, A., additional, Potluri, S., additional, Matthiesen, J., additional, Mather, M., additional, Taleongpong, P., additional, Chaston, R., additional, Silmon, A., additional, Curtis, A., additional, Lindsey, J. C., additional, Crosier, S., additional, Smith, A. J., additional, Goschzik, T., additional, Doz, F., additional, Rutkowski, S., additional, Lannering, B., additional, Pietsch, T., additional, Bailey, S., additional, Williamson, D., additional, and Clifford, S. C., additional

Published
2017
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21. Adsorbed Organic Material and Its Control on Wettability

Author

Matthiesen, J., Hassenkam, T., Bovet, N., Dalby, K. N., and Stipp, S. L. S.

Abstract

Laboratory core flood and field scale tests have demonstrated that 5–40% more oil can be released from sandstone reservoirs by injecting low salinity water, rather than high salinity fluids, such as seawater or formation water. The effect has been explained by a change in wettability of the minerals that form the pore surfaces, as a result of the decrease in divalent cation concentration. We have previously demonstrated that, even for solvent cleaned core samples, mineral surfaces retain a significant quantity of carbon containing material and this affects wettability and response to changed salinity. Here we quantified the response of sandstone core plug material in its preserved state (i.e., after storage in kerosene) and after the same core plug material was treated with ethanol and ozone to remove adsorbed organic compounds. We used the chemical force microscopy (CFM) mode of atomic force microscopy (AFM) to directly measure the adhesion force for two types of molecules on pore surfaces of individual sand grains that were plucked from an oil reservoir core plug. We functionalized AFM tips with alkane or carboxylate, so they resembled tiny oil droplets and measured adhesion to the sand grain surfaces in artificial seawater (ASW; 35,600 ppm) and in ASW diluted to ∼1,500 ppm (ASW-low). Both before and after the ethanol/ozone treatment, and for both the alkane and the carboxylate functionalized tips, the adhesion was lower in ASW diluted to ∼1,500 ppm than in ASW. For both alkane and carboxylate, the difference in adhesion between ASW and ASW-low was higher before the ethanol/ozone treatment. We attribute this change in response to the salinity dependent force caused mainly by the electric double layer (EDL) at the sand grain surfaces. We interpret the higher adhesion difference, before a very thorough ethanol/ozone treatment, to be a result of the loss of the organic material that was originally adsorbed on these surfaces, which adds to the charge density and thereby to the salinity dependent EDL force. Investigating the same area on the same pore surface, before and after removal of the organic material, demonstrates without doubt that it is organic material that causes the low salinity response, not the underlying mineral surface.

Published
2024
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22. Routine molecular subgrouping of medulloblastoma: Bridging the divide between research and the clinic using low-cost, mass spectrometry-based DNA methylomics

Author

Schwalbe, E., primary, Hicks, D., additional, Rafiee, G., additional, Bashton, M., additional, Gohlke, H., additional, Enshaei, A., additional, Potluri, S., additional, Matthiesen, J., additional, Mather, M., additional, Taleongpong, P., additional, Chaston, R., additional, Crosier, S., additional, Smith, A., additional, Williamson, D., additional, Bailey, S., additional, and Clifford, S., additional

Published
2016
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23. Could Atomic-Force Microscopy Force Mapping Be a Fast Alternative to Core-Plug Tests for Optimizing Injection-Water Salinity for Enhanced Oil Recovery in Sandstone?

Author

Hassenkam, T.., primary, Andersson, M. P., additional, Hilner, E.., additional, Matthiesen, J.., additional, Dobberschütz, S.., additional, Dalby, K. N., additional, Bovet, N.., additional, Stipp, S. L., additional, Salino, P.., additional, Reddick, C.., additional, and Collins, I. R., additional

Published
2016
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26. Oxidation of Pt(110)

Author

Li, W.X., Österlund, L., Vestergaard, E.K., Vang, R.T., Matthiesen, J., Pedersen, T.M., Lægsgaard, Erik, Hammer, B., and Besenbacher, F.

Published
2004

30. Observation of the low salinity effect by atomic force adhesion mapping on reservoir sandstones

Author

Hassenkam, T., Matthiesen, J., Pedersen, C. S., Dalby, K. N., Stipp, S. L.S., Collins, I. R., Hassenkam, T., Matthiesen, J., Pedersen, C. S., Dalby, K. N., Stipp, S. L.S., and Collins, I. R.

Abstract

Field tests have demonstrated that oil production from sandstone reservoirs increases when injected water salinity is low, i.e. -1500 ppm total dissolved solids (TDS). In core plug tests performed at reservoir conditions, low salinity flooding has been responsible for incremental recoveries ranging from about 5 to 38%. Previous work has suggested that for the low salinity effect to manifest itself, the oil must contain polar components, the formation water must contain divalent cations and clay must be present in the reservoir, but a clear understanding of the mechanism, from fundamental chemical and physical principals, is still subject to debate. In the work reported here, an atomic force microscope (AFM) has been used in force spectroscopy mode to investigate the nature and magnitude of the interaction between hydrocarbon molecules with carboxylic acid end groups and the pore surfaces of oil reservoir sandstones. By functionalizing the AFM tip with polar molecules we have been able to measure, quantitatively, the adhesion forces between these molecules and the mineral surfaces under 36,500 and 1500 ppm TDS artificial seawater (ASW) solutions. Collecting these measurements in two-dimensional arrays, known as force maps, revealed that adhesion was highest on the quartz grain surfaces during exposure to the high salinity solutions and it decreased when salinity decreased in nearly all cases. The drop in adhesion was observed through several high to low salinity cycles. We interpreted certain small features that were visible on the quartz surfaces to be clay that had grown directly on the sand grains from solution during diagenesis. Adhesion on these clay surfaces also changed with modifications in salinity. We observed no difference in behaviour whether the sandstone was preserved or cleaned; both types of core demonstrated a clear low salinity response.

Published
2012

35. Oxidation of Pt(110)

Author

Li, W X, Österlund, Lars, Vestergaard, E K, Vang, R T, Matthiesen, J, Pedersen, T M, Laegsgaard, E, Hammer, B, Besenbacher, F, Li, W X, Österlund, Lars, Vestergaard, E K, Vang, R T, Matthiesen, J, Pedersen, T M, Laegsgaard, E, Hammer, B, and Besenbacher, F

Abstract

Using scanning tunneling microscopy and temperature programed desorption we investigate the Pt(110) surface under strongly oxidizing conditions involving either high-pressure O-2 or atomic oxygen exposure. At low temperatures, only disordered Pt oxide structures are observed. After annealing ordered surface oxide islands are observed to coexist with a highly stable reconstructed (12x2)-O chemisorption structure. From density functional theory calculations a model for the surface oxide phase is revealed. The phase is found to be metastable, and its presence is explained in terms of stabilizing defects in the chemisorption layer and reduced Pt mobility.

Published
2004
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41. A search for solar-like oscillations in K giants in the globular cluster M 4

Author

Frandsen, S., primary, Bruntt, H., additional, Grundahl, F., additional, Kopacki, G., additional, Kjeldsen, H., additional, Arentoft, T., additional, Stello, D., additional, Bedding, T. R., additional, Jacob, A. P., additional, Gilliland, R. L., additional, Edmonds, P. D., additional, Michel, E., additional, and Matthiesen, J., additional

Published
2007
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44. Oxidation of Pt(110)

Author

Li, W. X., primary, Österlund, L., additional, Vestergaard, E. K., additional, Vang, R. T., additional, Matthiesen, J., additional, Pedersen, T. M., additional, Lægsgaard, E., additional, Hammer, B., additional, and Besenbacher, F., additional

Published
2004
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45. Interactions of Na, K, Mg2, and Ca2숫 Benzene Self-Assembled Monolayers.

Author

Rimmen, M., Matthiesen, J., Bovet, N., Hassenkam, T., Pedersen, C. S., and Stipp, S. L. S.

Subjects
*BENZENE, *MOLECULAR self-assembly, *MONOMOLECULAR films, *MOLECULAR interactions, *PROTEIN structure, *ATOMIC force microscopy
Abstract

Interactions between cations andorganic molecules are found throughoutnature, from the functionality and structure of proteins in humansand animals to the exchange of ions in minerals in soil and oil reservoirswith the fluid phases. We have explored the behavior of the s-blockelements that are most common in the natural world, namely, Na, K, Mg2, and Ca2. Specifically,we investigated how these ions affect the interactions between surfacescovered by self-assembled monolayers (SAMs) terminated with benzenemolecules. We used a flat oxidized silicon substrate and an atomicforce microscopy (AFM) tip that were both functionalized with 11-phenoxyundecane-1-thioland measured the adhesion force between them in solutions of eachof the four chloride salts. We observed that the adhesion increasedin the order of the Hofmeister series: K< Na≈ Mg2< Ca2. Supplementary evidencefrom X-ray photoelectron spectroscopy (XPS) allowed us to concludethat K温 in the benzene layers, creating a positivesurface charge on the benzene-covered surfaces, thus leading to loweradhesion in KCl solutions than in pure water. Evidence suggested thatCa2皇 not bind to the surfaces but forms bridges betweenthe layers, leading to higher adhesion than in pure water. In Na橷 Mg2늉溶⨧, adhesion is quite similarto that in pure water, indicating a lack of interaction between thesetwo ions and the surfaces, or at least that the interaction is tooweak to be detected by our measurements. The results of our studiesclearly show that even a nonpolar, hydrophobic molecule, such as benzene,has a role to play in the behavior of aqueous solutions and that itinteracts differently depending on which ions are present. Even ionsfrom the same column in the periodic table behave differently. [ABSTRACT FROM AUTHOR]

Published
2014
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