233 results on '"Diller, K."'
Search Results
52. Analysis of the Water Permeability of Human Granulocytes at Subzero Temperatures in the Presence of Extracellular Ice
- Author
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Schwartz, G. J. and Diller, K. R.
- Abstract
The plasma membrane water permeability of human granulocytes in the presence of extracellular ice was determined experimentally on a cryomicroscope. Transient volumes of individual cells were measured at constant subzero temperatures subsequent to ice nucleation. Permeability values were deduced by adjustment of multiple parameters in a model to obtain an optimal fit to the data. The permeability was determined to be a function of both temperature and intracellular solute osmolality, with a reference value at 0°C of 0.407 μm/atm·min and temperature and solute coefficients of 218kJ/mol and 1.09 Osm/kg.
- Published
- 1983
- Full Text
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53. Therapeutic Effects of Postburn Cooling
- Author
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Ross, D. C. and Diller, K. R.
- Abstract
The use of cooling as first aid in burn injury has been widely justified and employed although, at present, there exists no defined scientific verification of its physiological benefit or a rational therapeutic protocol to follow. The objective of this study was to identify and to quantify the primary parameters which control cooling therapy. Experiments were performed on over 200 hamster cheeckpouch preparations by creating a standard burn in the tissue resulting in the occlusion of a predictable percentage of vessels in the microcirculation. Following a delay of either 30 s or 10 min, the tissue was cooled to a temperature ranging between 3°C and 25°C for either 5, 30, or 60 min. In general, postburn cooling caused resumption of blood flow in a number of vessels which would otherwise have remained inactive. Optimum cooling temperatures were within the range of 5°C to 10°C, and were more effective when initiated immediately following the burn and maintained for times extended to 1 hr.
- Published
- 1978
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54. Measurement of Burn-Induced Leakage of Macromolecules in Living Tissue
- Author
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Green, D. M. and Diller, K. R.
- Abstract
An experimental technique has been developed to measure changes in vascular permeability caused by thermal trauma to the microvascular bed of the hamster cheek pouch. A solution of flourescein isothiocyanate (FITC) conjugated dextran was injected directly into the circulatory system. Subsequent leakage of dye from vessels into the extravascular space was directly observed by light microscopy and recorded by sequential photography. Individual frames of the filmed record of the trauma and post-trauma process were digitized and analyzed by computer. A point-by-point densitometric evaluation of the digitized image provides a measure of extravascular accumulation of dye-tagged dextran. Preliminary results indicate that preburn treatment with large doses of heparin yields a significant reduction in burn-induced edema.
- Published
- 1978
- Full Text
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55. Analysis of volumetric changes in rat pancreatic islets under osmotic stress using laser scanning confocal microscopy
- Author
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Merchant, F. A., Aggarwal, S. J., Diller, K. R., Bartels, K. A., and Alan Bovik
56. The contribution of vacancy defects to mass transport in alkali halides-an assessment using theoretical calculations of defect energies
- Author
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Catlow, C R A, primary, Corish, J, additional, Diller, K M, additional, Jacobs, P W M, additional, and Norgett, M J, additional
- Published
- 1979
- Full Text
- View/download PDF
57. Blood Freezing to Nearly Absolute Zero Temperature: −272.29°C
- Author
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Cravalho, E. G., primary, Huggins, C. E., additional, Diller, K. R., additional, and Watson, W. W., additional
- Published
- 1981
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58. A THEORETICAL STUDY OF INTRINSIC AND EXTRINSIC DEFECT PROPERTIES OF ALKALI HALIDES
- Author
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CATLOW, C. R.A., primary, CORISH, J., additional, DILLER, K. M., additional, JACOBS, P. W.M., additional, and NORGETT, M. J., additional
- Published
- 1976
- Full Text
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59. Interstitial defects in irradiated alkali halides
- Author
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Catlow, C R A, primary, Diller, K M, additional, and Norgett, M J, additional
- Published
- 1975
- Full Text
- View/download PDF
60. Off-center displacements of univalent impurity ions in alkali-halide crystals
- Author
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Catlow, C. R. A., primary, Diller, K. M., additional, Norgett, M. J., additional, Corish, J., additional, Parker, B. M. C., additional, and Jacobs, P. W. M., additional
- Published
- 1978
- Full Text
- View/download PDF
61. Volumetric changes in Saccharomyces cerevisiae during freezing at constant cooling rates
- Author
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Ushiyama, M., primary, Cravalho, E., additional, and Diller, K., additional
- Published
- 1972
- Full Text
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62. Comparison Of Student Learning In Challenge Based And Traditional Instruction In Biotransport Engineering Classrooms
- Author
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Rivale, Stephanie, primary, Martin, Taylor, additional, and Diller, K., additional
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63. Evolution of Biomedical Engineering Students’ Perceptions of Problem Solving and Instruction Strategies During a Challenge-Based Instruction Course
- Author
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Clegg, John, primary and Diller, K. R., additional
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64. Karly and the ketogenic diet.
- Author
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Diller K
- Published
- 2003
65. Unconventional spin relaxation involving localized vibrational modes in Ho single-atom magnets
- Author
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Marina Pivetta, Dominik M. Juraschek, E. Velez-Fort, Jan Dreiser, Kurt Kummer, Sebastian Stepanow, Nicola A. Spaldin, Aparajita Singha, Stefano Rusponi, Katharina Diller, Corneliu Nistor, Pietro Gambardella, Fabio Donati, Romana Baltic, Christian Wäckerlin, Luca Persichetti, Harald Brune, Donati, F., Rusponi, S., Stepanow, S., Persichetti, L., Singha, A., Juraschek, D. M., Wäckerlin, C., Baltic, R., Pivetta, M., Diller, K., Nistor, C., Dreiser, J., Kummer, K., Velez-Fort, E., Spaldin, N. A., Brune, H., and Gambardella, P.
- Subjects
Materials science ,Field (physics) ,bistability ,high-field ,General Physics and Astronomy ,anisotropy ,magnetization ,01 natural sciences ,symbols.namesake ,0103 physical sciences ,Atom ,dichroism ,010306 general physics ,Settore FIS/03 ,Condensed matter physics ,remanence ,temperature ,blocking ,Magnetic field ,molecule magnet ,lattice-relaxation ,Magnet ,Molecular vibration ,symbols ,Relaxation (physics) ,Density functional theory ,Raman spectroscopy - Abstract
We investigate the spin relaxation of Ho single atom magnets on $\mathrm{MgO}/\mathrm{Ag}(100)$ as a function of temperature and magnetic field. We find that the spin relaxation is thermally activated at low field, while it remains larger than 1000 s up to 30 K and 8 T. This behavior contrasts with that of single molecule magnets and bulk paramagnetic impurities, which relax faster at high field. Combining our results with density functional theory, we rationalize this unconventional behavior by showing that local vibrations activate a two-phonon Raman process with a relaxation rate that peaks near zero field and is suppressed at high field. Our work shows the importance of these excitations in the relaxation of axially coordinated magnetic atoms.
- Published
- 2020
66. Magnetic properties of on-surface synthesized single-ion molecular magnets
- Author
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Stefano Rusponi, Marina Pivetta, Raphael Hellwig, E. Velez-Fort, Jan Dreiser, Aparajita Singha, Katharina Diller, Luca Floreano, Albano Cossaro, Alberto Verdini, Christian Wäckerlin, Harald Brune, Diller, K., Singha, A., Pivetta, M., Wackerlin, C., Hellwig, R., Verdini, A., Cossaro, A., Floreano, L., Velez-Fort, E., Dreiser, J., Rusponi, S., and Brune, H.
- Subjects
metal-free ,spectroscopy ,Materials science ,molecular magnets ,on-surface synthesis ,Magnetism ,electronic-structure ,General Chemical Engineering ,02 engineering and technology ,010402 general chemistry ,spin ,porphyrins ,01 natural sciences ,law.invention ,chemistry.chemical_compound ,Adsorption ,law ,Molecule ,Thin film ,scanning-tunneling-microscopy ,complexes ,submonolayer ,Phthalocyanine ,General Chemistry ,021001 nanoscience & nanotechnology ,Magnetic hysteresis ,equipment and supplies ,molecular magnet ,0104 chemical sciences ,Crystallography ,thin-film ,chemistry ,Magnet ,Scanning tunneling microscope ,0210 nano-technology ,human activities - Abstract
We perform on-surface synthesis of single-ion molecular magnets on an Ag(111) surface and characterize their morphology, chemistry, and magnetism. The first molecule we synthesize is TbPc2 to enable comparison with chemically synthesized and subsequently surface adsorbed species. We demonstrate the formation of TbPc2 with a yield close to 100% and show that on-surface synthesis leads to identical magnetic and morphological properties compared to the previously studied chemically synthesized species. Moreover, exposure of the surface adsorbed TbPc2 molecules to air does not modify their magnetic and morphological properties. To demonstrate the versatility of our approach, we synthesize novel Tb double deckers using tert-butyl-substituted phthalocyanine (tbu-2H-Pc). The Tb(tbu-Pc)(2) molecules exhibit magnetic hysteresis and therefore are the first purely on-surface synthesized single ion magnet.
- Published
- 2019
67. Magnetic remanence in single atoms
- Author
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François Patthey, Luca Persichetti, Pietro Gambardella, Fabio Donati, Aparajita Singha, Katharina Diller, Romana Baltic, Harald Brune, Jan Dreiser, Sebastian Stepanow, Kurt Kummer, Stefano Rusponi, Edgar Fernandes, Corneliu Nistor, Christian Wäckerlin, Željko Šljivančanin, Donati, F., Rusponi, S., Stepanow, S., Wäckerlin, C., Singha, A., Persichetti, L., Baltic, R., Diller, K., Patthey, F., Fernandes, E., Dreiser, J., Šljivančanin, Å., Kummer, K., Nistor, C., Gambardella, P., and Brune, H.
- Subjects
Multidisciplinary ,Settore FIS/03 ,Condensed matter physics ,Chemistry ,chemistry.chemical_element ,02 engineering and technology ,Decoupling (cosmology) ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,Condensed Matter::Materials Science ,Remanence ,Magnet ,Condensed Matter::Superconductivity ,0103 physical sciences ,Atom ,010306 general physics ,0210 nano-technology ,Spin (physics) ,Ground state ,Holmium - Abstract
Stable magnets from single atoms An important goal in molecular magnetism is to create a permanent magnet from a single atom. Metal atoms adsorbed on surfaces can develop strong magnetization in an applied field (paramagnetism). Donati et al. show that single holmium atoms adsorbed on a magnesium oxide film grown on a silver substrate show residual magnetism for temperatures up to 30 K and bistabilty that lasts for 1500 s at 10 K (see the Perspective by Khajetoorians and Heinrich). The atom avoids spin relaxation by a combination of quantum-state symmetry and by the oxide film preventing the spin from interacting with the underlying metal via tunneling. Science , this issue p. 318 ; see also p. 296
- Published
- 2016
68. Magnetic properties of on-surface synthesized single-ion molecular magnets.
- Author
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Diller K, Singha A, Pivetta M, Wäckerlin C, Hellwig R, Verdini A, Cossaro A, Floreano L, Vélez-Fort E, Dreiser J, Rusponi S, and Brune H
- Abstract
We perform on-surface synthesis of single-ion molecular magnets on an Ag(111) surface and characterize their morphology, chemistry, and magnetism. The first molecule we synthesize is TbPc
2 to enable comparison with chemically synthesized and subsequently surface adsorbed species. We demonstrate the formation of TbPc2 with a yield close to 100% and show that on-surface synthesis leads to identical magnetic and morphological properties compared to the previously studied chemically synthesized species. Moreover, exposure of the surface adsorbed TbPc2 molecules to air does not modify their magnetic and morphological properties. To demonstrate the versatility of our approach, we synthesize novel Tb double deckers using tert -butyl-substituted phthalocyanine (tbu-2H-Pc). The Tb(tbu-Pc)2 molecules exhibit magnetic hysteresis and therefore are the first purely on-surface synthesized single ion magnet., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)- Published
- 2019
- Full Text
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69. Understanding the Superior Stability of Single-Molecule Magnets on an Oxide Film.
- Author
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Studniarek M, Wäckerlin C, Singha A, Baltic R, Diller K, Donati F, Rusponi S, Brune H, Lan Y, Klyatskaya S, Ruben M, Seitsonen AP, and Dreiser J
- Abstract
The stability of magnetic information stored in surface adsorbed single-molecule magnets is of critical interest for applications in nanoscale data storage or quantum computing. The present study combines X-ray magnetic circular dichroism, density functional theory and magnetization dynamics calculations to gain deep insight into the substrate dependent relevant magnetization relaxation mechanisms. X-ray magnetic circular dichroism reveals the opening of a butterfly-shaped magnetic hysteresis of DyPc
2 molecules on magnesium oxide and a closed loop on the bare silver substrate, while density functional theory shows that the molecules are only weakly adsorbed in both cases of magnesium oxide and silver. The enhanced magnetic stability of DyPc2 on the oxide film, in conjunction with previous experiments on the TbPc2 analogue, points to a general validity of the magnesium oxide induced stabilization effect. Magnetization dynamics calculations reveal that the enhanced magnetic stability of DyPc2 and TbPc2 on the oxide film is due to the suppression of two-phonon Raman relaxation processes. The results suggest that substrates with low phonon density of states are beneficial for the design of spintronics devices based on single-molecule magnets., Competing Interests: The authors declare no conflict of interest., (© 2019 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.)- Published
- 2019
- Full Text
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70. A Review of Hot Beverage Temperatures-Satisfying Consumer Preference and Safety.
- Author
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Abraham J and Diller K
- Subjects
- Consumer Product Safety, Cooking, Hot Temperature, Humans, Satiety Response, Beverages analysis, Consumer Behavior
- Abstract
Hot beverages are served ubiquitously in the food-service industry as well as at residences and other venues. Coffee and tea beverages, in particular, are brewed at temperatures that are sufficiently high to cause immediate and serious risk for scald injuries. On the other hand, numerous research studies have been performed to identify the preferred consumption temperatures for hot beverages. The outcome of these mutually reinforcing studies is that the preferred drinking temperatures are significantly below the often-encountered brewing temperatures (∼200 °F). Consequently, there is great need to distinguish brewing temperatures from serving temperatures. Serving consumers beverages at very high temperatures is not only unnecessary (from a preference standpoint) but also unsafe. An appropriate range for service temperatures is (130 to 160 °F). PRACTICAL APPLICATION: Often times, hot beverages are served at temperatures near their brewing temperature; far hotter than preferred by consumers. This practice creates unnecessary risk to the consumer. A more rationale recommended range of service temperatures is 130 to 160 °F. This recommendation balances a range of consumer preferences and safety., (© 2019 Institute of Food Technologists®.)
- Published
- 2019
- Full Text
- View/download PDF
71. Isomerism control of diethylstilbestrol by metal surface induced O-H cleavage.
- Author
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Oh SC, Lloyd JA, Fischer S, Saglam Ö, Papageorgiou AC, Diller K, Duncan DA, Klappenberger F, Allegretti F, Reichert J, and Barth JV
- Abstract
Diethylstilbestrol (DES) is studied on Ag(111) and Cu(111) surfaces using X-ray photoelectron spectroscopy (XPS) and scanning tunnelling microscopy (STM). We find that DES molecules on the silver surface adsorb intact and adopt a trans-conformation. On the more reactive copper surface, O-H bond cleavage results in molecular adsorption in the cis-conformation, thus providing the means of obtaining different adsorption geometries. The difference in isomerism is reflected in the observed self-assemblies which exhibit room-temperature stability.
- Published
- 2018
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72. Stretchable Tattoo-Like Heater with On-Site Temperature Feedback Control.
- Author
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Stier A, Halekote E, Mark A, Qiao S, Yang S, Diller K, and Lu N
- Abstract
Wearable tissue heaters can play many important roles in the medical field. They may be used for heat therapy, perioperative warming and controlled transdermal drug delivery, among other applications. State-of-the-art heaters are too bulky, rigid, or difficult to control to be able to maintain long-term wearability and safety. Recently, there has been progress in the development of stretchable heaters that may be attached directly to the skin surface, but they often use expensive materials or processes and take significant time to fabricate. Moreover, they lack continuously active, on-site, unobstructive temperature feedback control, which is critical for accommodating the dynamic temperatures required for most medical applications. We have developed, fabricated and tested a cost-effective, large area, ultra-thin and ultra-soft tattoo-like heater that has autonomous proportional-integral-derivative (PID) temperature control. The device comprises a stretchable aluminum heater and a stretchable gold resistance temperature detector (RTD) on a soft medical tape as fabricated using the cost and time effective "cut-and-paste" method. It can be noninvasively laminated onto human skin and can follow skin deformation during flexure without imposing any constraint. We demonstrate the device's ability to maintain a target temperature typical of medical uses over extended durations of time and to accurately adjust to a new set point in process. The cost of the device is low enough to justify disposable use., Competing Interests: The authors declare no conflict of interest.
- Published
- 2018
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73. Interpretation of x-ray absorption spectroscopy in the presence of surface hybridization.
- Author
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Diller K, Maurer RJ, Müller M, and Reuter K
- Abstract
X-ray absorption spectroscopy (XAS) yields direct access to the electronic and geometric structure of hybrid inorganic-organic interfaces formed upon adsorption of complex molecules at metal surfaces. The unambiguous interpretation of corresponding spectra is challenged by the intrinsic geometric flexibility of the adsorbates and the chemical interactions with the interface. Density-functional theory (DFT) calculations of the extended adsorbate-substrate system are an established tool to guide peak assignment in X-ray photoelectron spectroscopy of complex interfaces. We extend this to the simulation and interpretation of XAS data in the context of functional organic molecules on metal surfaces using dispersion-corrected DFT calculations within the transition potential approach. For the prototypical case of 2H-porphine adsorbed on Ag(111) and Cu(111) substrates, we follow the two main effects of the molecule/surface interaction onto the X-ray absorption signatures: (1) the substrate-induced chemical shift of the 1s core levels that dominates in physisorbed systems and (2) the hybridization-induced broadening and loss of distinct resonances that dominate in more chemisorbed systems.
- Published
- 2017
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74. Giant Hysteresis of Single-Molecule Magnets Adsorbed on a Nonmagnetic Insulator.
- Author
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Wäckerlin C, Donati F, Singha A, Baltic R, Rusponi S, Diller K, Patthey F, Pivetta M, Lan Y, Klyatskaya S, Ruben M, Brune H, and Dreiser J
- Abstract
TbPc2 single-molecule magnets adsorbed on a magnesium oxide tunnel barrier exhibit record magnetic remanence, record hysteresis opening, perfect out-of-plane alignment of the magnetic easy axes, and self-assembly into a well-ordered layer., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2016
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75. Single-Molecule Magnets: Giant Hysteresis of Single-Molecule Magnets Adsorbed on a Nonmagnetic Insulator (Adv. Mater. 26/2016).
- Author
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Wäckerlin C, Donati F, Singha A, Baltic R, Rusponi S, Diller K, Patthey F, Pivetta M, Lan Y, Klyatskaya S, Ruben M, Brune H, and Dreiser J
- Abstract
In Tb(Pc)2 single-molecule magnets, where Pc is phthalocyanine, adsorbed on magnesium oxide, the fluctuations of the terbium magnetic moment are strongly suppressed in contrast to the adsorption on silver. On page 5195, J. Dreiser and co-workers investigate that the molecules are perfectly organized by self-assembly, as seen in the scanning tunnelling microscopy image (top part of the design). The molecules are probed by circularly polarized X-rays depicted as green spirals., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)
- Published
- 2016
- Full Text
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76. In vacuo interfacial tetrapyrrole metallation.
- Author
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Diller K, Papageorgiou AC, Klappenberger F, Allegretti F, Barth JV, and Auwärter W
- Abstract
The metallation of tetrapyrroles at well-defined surfaces under ultra-high vacuum conditions represents an unconventional synthesis approach to achieve tetrapyrrole-based metal-organic complexes and architectures. Different protocols, pioneered over the last decade, and now widely applied in several fields, provide an elegant route to metallo-tetrapyrrole systems often elusive to conventional procedures and give access and exquisite insight into on-surface tetrapyrrole chemistry. As highlighted by the functionality of metallo-porphyrins in biological or other environments and by the eminent role of metallo-phthalocyanines in synthetic materials, the control on the metal centres incorporated into the macrocycle is of utmost importance to achieve tailored properties in tetrapyrrole-based nanosystems. In the on-surface scenario, precise metallation pathways were developed, including reactions of tetrapyrroles with metals supplied by physical vapour deposition, chemical vapour deposition or the tip of a scanning tunnelling microscope, and self-metallation by atoms of an underlying support. Herein, we provide a comprehensive overview of in vacuo tetrapyrrole metallation, addressing two-dimensional as well as three-dimensional systems. Furthermore, we comparatively assess the available library of on-surface metallation protocols and elaborate on the state-of-the-art methodology.
- Published
- 2016
- Full Text
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77. Dynamics of Spatially Confined Bisphenol A Trimers in a Unimolecular Network on Ag(111).
- Author
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Lloyd JA, Papageorgiou AC, Fischer S, Oh SC, Saǧlam Ö, Diller K, Duncan DA, Allegretti F, Klappenberger F, Stöhr M, Maurer RJ, Reuter K, Reichert J, and Barth JV
- Abstract
Bisphenol A (BPA) aggregates on Ag(111) shows a polymorphism between two supramolecular motifs leading to formation of distinct networks depending on thermal energy. With rising temperature a dimeric pairing scheme reversibly converts into a trimeric motif, which forms a hexagonal superstructure with complex dynamic characteristics. The trimeric arrangements notably organize spontaneously into a self-assembled one-component array with supramolecular BPA rotors embedded in a two-dimensional stator sublattice. By varying the temperature, the speed of the rotors can be controlled as monitored by direct visualization. A combination of scanning tunneling microscopy and dispersion-corrected density-functional tight-binding (DFTB-vdW(surf)) based molecular modeling reveals the exact atomistic position of each molecule within the assembly as well as the driving force for the formation of the supramolecular rotors.
- Published
- 2016
- Full Text
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78. Spin Manipulation by Creation of Single-Molecule Radical Cations.
- Author
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Karan S, Li N, Zhang Y, He Y, Hong IP, Song H, Lü JT, Wang Y, Peng L, Wu K, Michelitsch GS, Maurer RJ, Diller K, Reuter K, Weismann A, and Berndt R
- Abstract
All-trans-retinoic acid (ReA), a closed-shell organic molecule comprising only C, H, and O atoms, is investigated on a Au(111) substrate using scanning tunneling microscopy and spectroscopy. In dense arrays single ReA molecules are switched to a number of states, three of which carry a localized spin as evidenced by conductance spectroscopy in high magnetic fields. The spin of a single molecule may be reversibly switched on and off without affecting its neighbors. We suggest that ReA on Au is readily converted to a radical by the abstraction of an electron.
- Published
- 2016
- Full Text
- View/download PDF
79. Interfacial charge rearrangement and intermolecular interactions: Density-functional theory study of free-base porphine adsorbed on Ag(111) and Cu(111).
- Author
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Müller M, Diller K, Maurer RJ, and Reuter K
- Abstract
We employ dispersion-corrected density-functional theory to study the adsorption of tetrapyrrole 2H-porphine (2H-P) at Cu(111) and Ag(111). Various contributions to adsorbate-substrate and adsorbate-adsorbate interactions are systematically extracted to analyze the self-assembly behavior of this basic building block to porphyrin-based metal-organic nanostructures. This analysis reveals a surprising importance of substrate-mediated van der Waals interactions between 2H-P molecules, in contrast to negligible direct dispersive interactions. The resulting net repulsive interactions rationalize the experimentally observed tendency for single molecule adsorption.
- Published
- 2016
- Full Text
- View/download PDF
80. Polyphenylsilole multilayers--an insight from X-ray electron spectroscopy and density functional theory.
- Author
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Diller K, Ma Y, Luo Y, Allegretti F, Liu J, Tang BZ, Lin N, Barth JV, and Klappenberger F
- Abstract
We present a combined investigation by means of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy of condensed multilayers of two polyphenylsiloles, namely hexaphenylsilole (HPS) and tetraphenylsilole (TPS). Both compounds exhibit very similar spectroscopic signatures, whose interpretation is aided by density functional theory (DFT) calculations. High-resolution XPS spectra of the Si 2p and C 1s core levels of these multilayers indicate a positively charged silicon ion flanked by two negatively charged adjacent carbon atoms in the silole core of both molecules. This result is corroborated quantitatively by DFT calculations on isolated HPS (TPS) molecules, which show a natural bond orbital partial charge of +1.67 e (+1.58 e) on the silicon and -0.34 e (-0.58 e) on the two neighbouring carbon atoms in the silole ring. These charges are conserved in direct contact with a Cu(111) substrate for films of submonolayer coverage, as evidenced by the Si 2p XPS data. The C K-edge NEXAFS spectra of HPS and TPS multilayers exhibit distinct and differing features. Their main characteristics reappear in the simulated spectra and are assigned to the different inequivalent carbon species in the molecule. The angle-dependent measurements hardly reveal any dichroism, i.e., the molecular π-systems are not uniformly oriented parallel or perpendicular with respect to the surface. Changes in the growth conditions of TPS, i.e., a reduction of the substrate temperature from 240 K to 80 K during deposition, lead to a broadening of both XPS and NEXAFS signatures, as well as an upward shift of the Si 2p and C 1s binding energies, indicative of a less ordered growth mode at low temperature.
- Published
- 2015
- Full Text
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81. Temperature-dependent templated growth of porphine thin films on the (111) facets of copper and silver.
- Author
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Diller K, Klappenberger F, Allegretti F, Papageorgiou AC, Fischer S, Duncan DA, Maurer RJ, Lloyd JA, Oh SC, Reuter K, and Barth JV
- Abstract
The templated growth of the basic porphyrin unit, free-base porphine (2H-P), is characterized by means of X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) spectroscopy measurements and density functional theory (DFT). The DFT simulations allow the deconvolution of the complex XPS and NEXAFS signatures into contributions originating from five inequivalent carbon atoms, which can be grouped into C-N and C-C bonded species. Polarization-dependent NEXAFS measurements reveal an intriguing organizational behavior: On both Cu(111) and Ag(111), for coverages up to one monolayer, the molecules adsorb undeformed and parallel to the respective metal surface. Upon increasing the coverage, however, the orientation of the molecules in the thin films depends on the growth conditions. Multilayers deposited at low temperatures exhibit a similar average tilting angle (30° relative to the surface plane) on both substrates. Conversely, for multilayers grown at room temperature a markedly different scenario exists. On Cu(111) the film thickness is self-limited to a coverage of approximately two layers, while on Ag(111) multilayers can be grown easily and, in contrast to the bulk 2H-P crystal, the molecules are oriented perpendicular to the surface. This difference in molecular orientation results in a modified line-shape of the C 1s XPS signatures, which depends on the incident photon energy and is explained by comparison with depth-resolved DFT calculations. Simulations of ionization energies for differently stacked molecules show no indication for a packing-induced modification of the multilayer XP spectra, thus indicating that the comparison of single molecule calculations to multilayer data is justified.
- Published
- 2014
- Full Text
- View/download PDF
82. Surface-assisted dehydrogenative homocoupling of porphine molecules.
- Author
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Wiengarten A, Seufert K, Auwärter W, Ecija D, Diller K, Allegretti F, Bischoff F, Fischer S, Duncan DA, Papageorgiou AC, Klappenberger F, Acres RG, Ngo TH, and Barth JV
- Subjects
- Dimerization, Microscopy, Scanning Tunneling, Nanostructures chemistry, Photoelectron Spectroscopy, Porphyrins metabolism, Silver chemistry, X-Ray Absorption Spectroscopy, Porphyrins chemistry
- Abstract
The templated synthesis of porphyrin dimers, oligomers, and tapes has recently attracted considerable interest. Here, we introduce a clean, temperature-induced covalent dehydrogenative coupling mechanism between unsubstituted free-base porphine units yielding dimers, trimers, and larger oligomers directly on a Ag(111) support under ultrahigh-vacuum conditions. Our multitechnique approach, including scanning tunneling microscopy, near-edge X-ray absorption fine structure and photoelectron spectroscopy complemented by theoretical modeling, allows a comprehensive characterization of the resulting nanostructures and sheds light on the coupling mechanism. We identify distinct coupling motifs and report a decrease of the electronic gap and a modification of the frontier orbitals directly associated with the formation of triply fused dimeric species. This new on-surface homocoupling protocol yields covalent porphyrin nanostructures addressable with submolecular resolution and provides prospective model systems towards the exploration of extended oligomers with tailored chemical and physical properties.
- Published
- 2014
- Full Text
- View/download PDF
83. Photoinduced C-C reactions on insulators toward photolithography of graphene nanoarchitectures.
- Author
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Palma CA, Diller K, Berger R, Welle A, Björk J, Cabellos JL, Mowbray DJ, Papageorgiou AC, Ivleva NP, Matich S, Margapoti E, Niessner R, Menges B, Reichert J, Feng X, Räder HJ, Klappenberger F, Rubio A, Müllen K, and Barth JV
- Abstract
On-surface chemistry for atomically precise sp(2) macromolecules requires top-down lithographic methods on insulating surfaces in order to pattern the long-range complex architectures needed by the semiconductor industry. Here, we fabricate sp(2)-carbon nanometer-thin films on insulators and under ultrahigh vacuum (UHV) conditions from photocoupled brominated precursors. We reveal that covalent coupling is initiated by C-Br bond cleavage through photon energies exceeding 4.4 eV, as monitored by laser desorption ionization (LDI) mass spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) gives insight into the mechanisms of C-Br scission and C-C coupling processes. Further, unreacted material can be sublimed and the coupled sp(2)-carbon precursors can be graphitized by e-beam treatment at 500 °C, demonstrating promising applications in photolithography of graphene nanoarchitectures. Our results present UV-induced reactions on insulators for the formation of all sp(2)-carbon architectures, thereby converging top-down lithography and bottom-up on-surface chemistry into technology.
- Published
- 2014
- Full Text
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84. Control of molecular organization and energy level alignment by an electronically nanopatterned boron nitride template.
- Author
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Joshi S, Bischoff F, Koitz R, Ecija D, Seufert K, Seitsonen AP, Hutter J, Diller K, Urgel JI, Sachdev H, Barth JV, and Auwärter W
- Abstract
Suitable templates to steer the formation of nanostructure arrays on surfaces are indispensable in nanoscience. Recently, atomically thin sp(2)-bonded layers such as graphene or boron nitride (BN) grown on metal supports have attracted considerable interest due to their potential geometric corrugation guiding the positioning of atoms, metallic clusters or molecules. Here, we demonstrate three specific functions of a geometrically smooth, but electronically corrugated, sp(2)/metal interface, namely, BN/Cu(111), qualifying it as a unique nanoscale template. As functional adsorbates we employed free-base porphine (2H-P), a prototype tetrapyrrole compound, and tetracyanoquinodimethane (TCNQ), a well-known electron acceptor. (i) The electronic moirons of the BN/Cu(111) interface trap both 2H-P and TCNQ, steering self-organized growth of arrays with extended molecular assemblies. (ii) We report an effective decoupling of the trapped molecules from the underlying metal support by the BN, which allows for a direct visualization of frontier orbitals by scanning tunneling microscopy (STM). (iii) The lateral molecular positioning in the superstructured surface determines the energetic level alignment; i.e., the energy of the frontier orbitals, and the electronic gap are tunable.
- Published
- 2014
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85. Self-assembly and chemical modifications of bisphenol a on Cu(111): interplay between ordering and thermally activated stepwise deprotonation.
- Author
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Fischer S, Papageorgiou AC, Lloyd JA, Oh SC, Diller K, Allegretti F, Klappenberger F, Seitsonen AP, Reichert J, and Barth JV
- Subjects
- Microscopy, Scanning Tunneling, Photoelectron Spectroscopy, Benzhydryl Compounds chemistry, Copper chemistry, Phenols chemistry, Protons
- Abstract
Bisphenol A (BPA) is a chemical widely used in the synthesis pathway of polycarbonates for the production of many daily used products. Besides other adverse health effects, medical studies have shown that BPA can cause DNA hypomethylation and therefore alters the epigenetic code. In the present work, the reactivity and self-assembly of the molecule was investigated under ultra-high-vacuum conditions on a Cu(111) surface. We show that the surface-confined molecule goes through a series of thermally activated chemical transitions. Scanning tunneling microscopy investigations showed multiple distinct molecular arrangements dependent on the temperature treatment and the formation of polymer-like molecular strings for temperatures above 470 K. X-ray photoelectron spectroscopy measurements revealed the stepwise deprotonation of the hydroxy groups, which allows the molecules to interact strongly with the underlying substrate as well as their neighboring molecules and therefore drive the organization into distinct structural arrangements. On the basis of the combined experimental evidence in conjunction with density functional theory calculations, structural models for the self-assemblies after the thermal treatment were elaborated.
- Published
- 2014
- Full Text
- View/download PDF
86. Self-terminating protocol for an interfacial complexation reaction in vacuo by metal-organic chemical vapor deposition.
- Author
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Papageorgiou AC, Fischer S, Oh SC, Sağlam O, Reichert J, Wiengarten A, Seufert K, Vijayaraghavan S, Ecija D, Auwärter W, Allegretti F, Acres RG, Prince KC, Diller K, Klappenberger F, and Barth JV
- Abstract
The fabrication and control of coordination compounds or architectures at well-defined interfaces is a thriving research domain with promise for various research areas, including single-site catalysis, molecular magnetism, light-harvesting, and molecular rotors and machines. To date, such systems have been realized either by grafting or depositing prefabricated metal-organic complexes or by protocols combining molecular linkers and single metal atoms at the interface. Here we report a different pathway employing metal-organic chemical vapor deposition, as exemplified by the reaction of meso-tetraphenylporphyrin derivatives on atomistically clean Ag(111) with a metal carbonyl precursor (Ru3(CO)12) under vacuum conditions. Scanning tunneling microscopy and X-ray spectroscopy reveal the formation of a meso-tetraphenylporphyrin cyclodehydrogenation product that readily undergoes metalation after exposure to the Ru-carbonyl precursor vapor and thermal treatment. The self-terminating porphyrin metalation protocol proceeds without additional surface-bound byproducts, yielding a single and thermally robust layer of Ru metalloporphyrins. The introduced fabrication scheme presents a new approach toward the realization of complex metal-organic interfaces incorporating metal centers in unique coordination environments.
- Published
- 2013
- Full Text
- View/download PDF
87. How surface bonding and repulsive interactions cause phase transformations: ordering of a prototype macrocyclic compound on Ag(111).
- Author
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Bischoff F, Seufert K, Auwärter W, Joshi S, Vijayaraghavan S, Écija D, Diller K, Papageorgiou AC, Fischer S, Allegretti F, Duncan DA, Klappenberger F, Blobner F, Han R, and Barth JV
- Subjects
- Binding Sites, Materials Testing, Particle Size, Phase Transition, Static Electricity, Surface Properties, Macrocyclic Compounds chemistry, Metal Nanoparticles chemistry, Metal Nanoparticles ultrastructure, Silver chemistry
- Abstract
We investigated the surface bonding and ordering of free-base porphine (2H-P), the parent compound of all porphyrins, on a smooth noble metal support. Our multitechnique investigation reveals a surprisingly rich and complex behavior, including intramolecular proton switching, repulsive intermolecular interactions, and density-driven phase transformations. For small concentrations, molecular-level observations using low-temperature scanning tunneling microscopy clearly show the operation of repulsive interactions between 2H-P molecules in direct contact with the employed Ag(111) surface, preventing the formation of islands. An increase of the molecular coverage results in a continuous decrease of the average intermolecular distance, correlated with multiple phase transformations: the system evolves from an isotropic, gas-like configuration via a fluid-like phase to a crystalline structure, which finally gives way to a disordered layer. Herein, considerable site-specific molecule-substrate interactions, favoring an exclusive adsorption on bridge positions of the Ag(111) lattice, play an important role. Accordingly, the 2D assembly of 2H-P/Ag(111) layers is dictated by the balance between adsorption energy maximization while retaining a single adsorption site counteracted by the repulsive molecule-molecule interactions. The long-range repulsion is associated with a charge redistribution at the 2H-P/Ag(111) interface comprising a partial filling of the lowest unoccupied molecular orbital, resulting in long-range electrostatic interactions between the adsorbates. Indeed, 2H-P molecules in the second layer that are electronically only weakly coupled to the Ag substrate show no repulsive behavior, but form dense-packed islands.
- Published
- 2013
- Full Text
- View/download PDF
88. Chemical transformations drive complex self-assembly of uracil on close-packed coinage metal surfaces.
- Author
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Papageorgiou AC, Fischer S, Reichert J, Diller K, Blobner F, Klappenberger F, Allegretti F, Seitsonen AP, and Barth JV
- Subjects
- Models, Molecular, Molecular Conformation, Quantum Theory, Spectrum Analysis, Surface Properties, Temperature, Copper chemistry, Silver chemistry, Uracil chemistry
- Abstract
We address the interplay of adsorption, chemical nature, and self-assembly of uracil on the Ag(111) and Cu(111) surfaces as a function of molecular coverage (0.3 to 1 monolayer) and temperature. We find that both metal surfaces act as templates and the Cu(111) surface acts additionally as a catalyst for the resulting self-assembled structures. With a combination of STM, synchrotron XPS, and NEXAFS studies, we unravel a distinct polymorphism on Cu(111), in stark contrast to what is observed for the case of uracil on the more inert Ag(111) surface. On Ag(111) uracil adsorbs flat and intact and forms close-packed two-dimensional islands. The self-assembly is driven by stable hydrogen-bonded dimers with poor two-dimensional order. On Cu(111) complex structures are observed exhibiting, in addition, a strong annealing temperature dependence. We determine the corresponding structural transformations to be driven by gradual deprotonation of the uracil molecules. Our XPS study reveals unambiguously the tautomeric signature of uracil in the contact layer and on Cu(111) the molecule's deprotonation sites. The metal-mediated deprotonation of uracil and the subsequent electron localization in the molecule determine important biological reactions. Our data show a dependence between molecular coverage and molecule-metal interaction on Cu(111), as the molecules tilt at higher coverages in order to accommodate a higher packing density. After deprotonation of both uracil N atoms, we observe an adsorption geometry that can be understood as coordinative anchoring with a significant charge redistribution in the molecule. DFT calculations are employed to analyze the surface bonding and accurately describe the pertaining electronic structure., (© 2012 American Chemical Society)
- Published
- 2012
- Full Text
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89. Homo-coupling of terminal alkynes on a noble metal surface.
- Author
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Zhang YQ, Kepčija N, Kleinschrodt M, Diller K, Fischer S, Papageorgiou AC, Allegretti F, Björk J, Klyatskaya S, Klappenberger F, Ruben M, and Barth JV
- Abstract
The covalent linking of acetylenes presents an important route for the fabrication of novel carbon-based scaffolds and two-dimensional materials distinct from graphene. To date few attempts have been reported to implement this strategy at well-defined interfaces or monolayer templates. Here we demonstrate through real space direct visualization and manipulation in combination with X-ray photoelectron spectroscopy and density functional theory calculations the Ag surface-mediated terminal alkyne C(sp)-H bond activation and concomitant homo-coupling in a process formally reminiscent of the classical Glaser-Hay type reaction. The alkyne homo-coupling takes place on the Ag(111) noble metal surface in ultrahigh vacuum under soft conditions in the absence of conventionally used transition metal catalysts and with volatile H(2) as the only by-product. With the employed multitopic ethynyl species, we demonstrate a hierarchic reaction pathway that affords discrete compounds or polymeric networks featuring a conjugated backbone. This presents a new approach towards on-surface covalent chemistry and the realization of two-dimensional carbon-rich or all-carbon polymers.
- Published
- 2012
- Full Text
- View/download PDF
90. Preserving charge and oxidation state of Au(III) ions in an agent-functionalized nanocrystal model system.
- Author
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Müllegger S, Schöfberger W, Rashidi M, Lengauer T, Klappenberger F, Diller K, Kara K, Barth JV, Rauls E, Schmidt WG, and Koch R
- Subjects
- Ligands, Models, Molecular, Molecular Conformation, Oxidation-Reduction, Drug Carriers chemistry, Gold chemistry, Metal Nanoparticles chemistry, Metalloporphyrins chemistry, Porphyrins chemistry
- Abstract
Supporting functional molecules on crystal facets is an established technique in nanotechnology. To preserve the original activity of ionic metallorganic agents on a supporting template, conservation of the charge and oxidation state of the active center is indispensable. We present a model system of a metallorganic agent that, indeed, fulfills this design criterion on a technologically relevant metal support with potential impact on Au(III)-porphyrin-functionalized nanoparticles for an improved anticancer-drug delivery. Employing scanning tunneling microscopy and -spectroscopy in combination with photoemission spectroscopy, we clarify at the single-molecule level the underlying mechanisms of this exceptional adsorption mode. It is based on the balance between a high-energy oxidation state and an electrostatic screening-response of the surface (image charge). Modeling with first principles methods reveals submolecular details of the metal-ligand bonding interaction and completes the study by providing an illustrative electrostatic model relevant for ionic metalorganic agent molecules, in general., (© 2011 American Chemical Society)
- Published
- 2011
- Full Text
- View/download PDF
91. Significant protection against high-dose simian immunodeficiency virus challenge conferred by a new prime-boost vaccine regimen.
- Author
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Schell JB, Rose NF, Bahl K, Diller K, Buonocore L, Hunter M, Marx PA, Gambhira R, Tang H, Montefiori DC, Johnson WE, and Rose JK
- Subjects
- Animals, Antibodies, Neutralizing blood, Gene Products, env genetics, Gene Products, env immunology, Gene Products, env metabolism, Gene Products, gag genetics, Gene Products, gag immunology, Gene Products, gag metabolism, Genetic Vectors administration & dosage, Immunization, Immunization, Secondary, Macaca mulatta, Neutralization Tests, SAIDS Vaccines genetics, SAIDS Vaccines immunology, Semliki forest virus genetics, Semliki forest virus metabolism, Simian Acquired Immunodeficiency Syndrome immunology, Simian Acquired Immunodeficiency Syndrome virology, Simian Immunodeficiency Virus genetics, Simian Immunodeficiency Virus metabolism, Simian Immunodeficiency Virus pathogenicity, Vesicular stomatitis Indiana virus genetics, Vesicular stomatitis Indiana virus metabolism, Viral Load, Antibodies, Viral blood, Genetic Vectors immunology, Immunization Schedule, SAIDS Vaccines administration & dosage, Simian Acquired Immunodeficiency Syndrome prevention & control, Simian Immunodeficiency Virus immunology
- Abstract
We constructed vaccine vectors based on live recombinant vesicular stomatitis virus (VSV) and a Semliki Forest virus (SFV) replicon (SFVG) that propagates through expression of the VSV glycoprotein (G). These vectors expressing simian immunodeficiency virus (SIV) Gag and Env proteins were used to vaccinate rhesus macaques with a new heterologous prime-boost regimen designed to optimize induction of antibody. Six vaccinated animals and six controls were then given a high-dose mucosal challenge with the diverse SIVsmE660 quasispecies. All control animals became infected and had peak viral RNA loads of 10(6) to 10(8) copies/ml. In contrast, four of the vaccinees showed significant (P = 0.03) apparent sterilizing immunity and no detectable viral loads. Subsequent CD8(+) T cell depletion confirmed the absence of SIV infection in these animals. The two other vaccinees had peak viral loads of 7 × 10(5) and 8 × 10(3) copies/ml, levels below those of all of the controls, and showed undetectable virus loads by day 42 postchallenge. The vaccine regimen induced high-titer prechallenge serum neutralizing antibodies (nAbs) to some cloned SIVsmE660 Env proteins, but antibodies able to neutralize the challenge virus swarm were not detected. The cellular immune responses induced by the vaccine were generally weak and did not correlate with protection. Although the immune correlates of protection are not yet clear, the heterologous VSV/SFVG prime-boost is clearly a potent vaccine regimen for inducing virus nAbs and protection against a heterogeneous viral swarm.
- Published
- 2011
- Full Text
- View/download PDF
92. Dynamic Data-Driven Finite Element Models for Laser Treatment of Cancer.
- Author
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Oden JT, Diller KR, Bajaj C, Browne JC, Hazle J, Babuška I, Bass J, Biduat L, Demkowicz L, Elliott A, Feng Y, Fuentes D, Prudhomme S, Rylander MN, Stafford RJ, and Zhang Y
- Abstract
Elevating the temperature of cancerous cells is known to increase their susceptibility to subsequent radiation or chemotherapy treatments, and in the case in which a tumor exists as a well-defined region, higher intensity heat sources may be used to ablate the tissue. These facts are the basis for hyperthermia based cancer treatments. Of the many available modalities for delivering the heat source, the application of a laser heat source under the guidance of real-time treatment data has the potential to provide unprecedented control over the outcome of the treatment process [7, 18]. The goals of this work are to provide a precise mathematical framework for the real-time finite element solution of the problems of calibration, optimal heat source control, and goal-oriented error estimation applied to the equations of bioheat transfer and demonstrate that current finite element technology, parallel computer architecture, data transfer infrastructure, and thermal imaging modalities are capable of inducing a precise computer controlled temperature field within the biological domain.
- Published
- 2007
- Full Text
- View/download PDF
93. Algae permeability to Me(2)SO from -3 to 23 degrees C.
- Author
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Tanaka JY, Walsh JR, Diller KR, Brand JJ, and Aggarwal SJ
- Subjects
- Biological Transport, Active, Chlorophyta cytology, Cryopreservation methods, Microscopy instrumentation, Models, Biological, Osmosis, Permeability, Temperature, Thermodynamics, Water metabolism, Chlorophyta metabolism, Cryoprotective Agents pharmacokinetics, Dimethyl Sulfoxide pharmacokinetics
- Abstract
Biphasic transport of water and dimethyl sulfoxide (Me(2)SO), a common cryoprotective agent (CPA), in algal cells was induced and measured on a cryoperfusion stage. A two-step experimental protocol provided data for the volumetric response of Chlorococcum (C.) texanum to impermeable and permeable solutes. First, the cells were exposed to a 500-mOsm sucrose solution, causing immediate shrinkage of the cell to a minimum equilibrium volume. Then an isoosmotic 200-mOsm/300-mOsm CPA/sucrose solution was introduced to the cells, resulting in increased cell volume to a new equilibrium state. Experiments were conducted at temperatures between -3 and 23 degrees C. Cell volumes were measured off-line by computer analysis of video images. A network thermodynamic model was fit to the transient volume data to determine permeabilities of C. texanum to water and Me(2)SO over the full temperature range, and results were calculated with two numeric methods. Biphasic transport was found to be slower at colder temperatures, with water entering the cell faster than Me(2)SO. Experimental results were also compared with data from similar experiments using methanol (MeOH) as the CPA. MeOH influx was calculated to be a magnitude larger than that of water. Additionally, MeOH permeability was at least three orders of magnitude greater than Me(2)SO permeability, and the difference in these solute permeabilities increased as temperature decreased., (Copyright 2001 Elsevier Science.)
- Published
- 2001
- Full Text
- View/download PDF
94. Model of human/liquid cooling garment interaction for space suit automatic thermal control.
- Author
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Nyberg KL, Diller KR, and Wissler EH
- Subjects
- Algorithms, Body Temperature physiology, Calibration, Ear Canal physiology, Energy Metabolism physiology, Environment, Controlled, Equipment Design, Humans, Skin Temperature physiology, Space Simulation, Thermometers, Body Temperature Regulation physiology, Models, Biological, Space Flight instrumentation, Space Suits
- Abstract
The Wissler human thermoregulation model was augmented to incorporate simulation of a space suit thermal control system that includes interaction with a liquid cooled garment (LCG) and ventilation gas flow through the suit. The model was utilized in the design process of an automatic controller intended to maintain thermal neutrality of an exercising subject wearing a liquid cooling garment. An experimental apparatus was designed and built to test the efficacy of specific physiological state measurements to provide feedback data for input to the automatic control algorithm. Control of the coolant inlet temperature to the LCG was based on evaluation of transient physiological parameters that describe the thermal state of the subject, including metabolic rate, skin temperatures, and core temperature. Experimental evaluation of the control algorithm function was accomplished in an environmental chamber under conditions that simulated the thermal environment of a space suit and transient metabolic work loads typical of astronaut extravehicular activity (EVA). The model was also applied to analyze experiments to evaluate performance of the automatic control system in maintaining thermal comfort during extensive transient metabolic profiles for a range of environmental temperatures. Finally, the model was used to predict the efficacy of the LCG thermal controller for providing thermal comfort for a variety of regiments that may be encountered in future space missions. Simulations with the Wissler model accurately predicted the thermal interaction between the subject and LCG for a wide range of metabolic profiles and environmental conditions and matched the function of the automatic temperature controller for inlet cooling water to the LCG.
- Published
- 2001
- Full Text
- View/download PDF
95. Automatic control of thermal neutrality for space suit applications using a liquid cooling garment.
- Author
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Nyberg KL, Diller KR, and Wissler EH
- Subjects
- Adult, Algorithms, Equipment Design, Female, Humans, Male, Middle Aged, Aerospace Medicine, Body Temperature Regulation, Space Suits
- Abstract
Background: Thermal control in the EVA spacesuit requires attention from the astronaut which is not always desirable or feasible. Improvements in thermal control involve implementation of an automatic thermal control system operating independently of the knowledge of the working astronaut., Methods: A control system was designed, developed, and tested to automatically maintain a subject's thermal neutrality while wearing a liquid cooling garment (LCG). Measurement of CO2 production as an indication of metabolic rate was used as a signal to initiate the control response. Mean body temperature, computed as a function of ear canal temperature and mean skin temperature, provided feedback to account for the thermal state of subjects as they were being cooled by the LCG. The control algorithm was tested on nine subjects, six males and three females, who performed a varying 90-min metabolic profile using an arm cranking ergometer. A total of 27 tests, three for each subject, were conducted in a thermal chamber at three different environmental temperatures: 10 degrees C, 18.3 degrees C and 26.7 degrees C., Results and Conclusions: Evaluation of subjective comfort rating and quantitative energy storage indicates good performance of the controller in maintaining thermal neutrality for the subject over a wide range of environmental and transient metabolic states. Measurements of metabolic rate effectively initiated controller response, and feedback of mean body temperature to the controller proved very capable of accounting for various steady-state environmental conditions and inter-subject variability.
- Published
- 2000
96. Issues in modeling thermal alterations in tissues.
- Author
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Diller KR and Pearce JA
- Subjects
- Animals, Burns classification, Burns pathology, Hot Temperature, Humans, Models, Biological, Burns physiopathology
- Abstract
Thermal injury in living tissues is commonly modeled as a rate process in which cell death is interpreted to occur as a function of a single kinetic process. Experimental data indicate that multiple rate processes govern the manifestation of injury and that these processes may act over a broad spectrum of time domains. Injury is typically computed as a dimensionless function (omega) of the temperature time history via an Arrhenius relationship to which numerical values are assigned based on defined threshold levels of damage. However, important issues central to calculation and interpretation of the omega function remain to be defined. These issues include the following: how is temperature identified in time and space within a tissue exposed to thermal stress; what is the biophysical and physiological meaning of a quantitative value for omega; how can omega be quantified in an experimental system; how should omega be scaled between graded levels of injury; and what are the differences in injury kinetics between unit volume- and unit surface area-governed processes of energy deposition into tissue to cause thermal stress? This paper addresses these issues with the goal of defining a more rigorous and comprehensive standard for modeling thermal injury in tissues.
- Published
- 1999
- Full Text
- View/download PDF
97. Development and solution of finite-difference equations for burn injury with spreadsheet software.
- Author
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Diller KR
- Subjects
- Finite Element Analysis, Humans, Microcomputers, Models, Biological, Burns, Software
- Abstract
This article presents a brief description of a set of equations by which the thermal burn process may be modeled, a formulation of the differential equations into a finite-difference format, and a simple method of solution using a standard commercial spreadsheet software application. A companion article provides a discussion of results that can be obtained with the modeling techniques presented here. A short version of the spreadsheet program is available from the author.
- Published
- 1999
- Full Text
- View/download PDF
98. Network thermodynamic model of coupled transport in a multicellular tissue--the islet of Langerhans.
- Author
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de Freitas RC, Diller KR, Lachenbruch CA, and Merchant FA
- Subjects
- Animals, Biological Transport, Biophysics methods, Cell Size, Cryopreservation methods, Electrolytes, In Vitro Techniques, Islets of Langerhans cytology, Mathematics, Rats, Solutions, Thermal Conductivity, Thermodynamics, Cryoprotective Agents pharmacokinetics, Dimethyl Sulfoxide pharmacokinetics, Islets of Langerhans physiology, Models, Biological
- Abstract
Network thermodynamic modeling via bond graphs was used to describe the water and cryoprotectant additive (CPA) transport in a multicellular tissue. The model is presented as a tool to understand the osmotic behavior of the islets of Langerhans when exposed to ternary aqueous solutions containing an electrolyte and a CPA. It accounts for the effects of the location of cells within the tissue and an interstitial matrix, plus differential permeabilities to water and CPA. The interstitial matrix was assumed to be a porous medium able to store the chemical species being transported. Controlled osmotic stress experiments were conducted on isolated rat pancreas islets to measure the transient volumetric response to step-wise changes in dimethyl sulfoxide, Me2SO, concentration. The model provides a tool for predicting the transient volumetric response of peripheral and interior cells and of interstitial tissue, as well as the build up of solute concentration, during addition and removal of CPAs and freezing and thawing protocols. Inverse solution methods were applied to determine values for standard cell membrane permeability parameters Lp, omega and sigma as well as for the interstitial flow conductivities Kw and Kp'.
- Published
- 1998
- Full Text
- View/download PDF
99. Sensitivity of kidney perfusion protocol design to physical and physiological parameters.
- Author
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Lachenbruch CA, Diller KR, and Pegg DE
- Subjects
- Animals, Capillary Permeability, Cell Membrane Permeability, Cryoprotective Agents, Glycerol, Mannitol, Microcirculation physiology, Perfusion methods, Cryopreservation methods, Kidney cytology, Kidney physiology, Liver Circulation physiology
- Abstract
The introduction and removal of cryoprotective agents (CPA) to a kidney via vascular perfusion may induce changes in cell volume that are destructive to the tubular epithelial or capillary endothelial cells as well as causing significant increases in vascular resistance that compromise the perfusion process. A network thermodynamic model of the coupled osmotic, hydrodynamic and elastic properties of the kidney was applied to evaluate the sensitivity of these critical outputs to a set of physiological and perfusion variables. Simulation results suggest that in the design of perfusion protocols for CPAs such as glycerol, it may be advantageous to: (a) select a CPA with as high a cell membrane permeability as possible; (b) increase the concentration of mannitol in the perfusate to about 200 mos/kg, beyond which there is no discernible benefit; (c) when glycerol is the CPA, limit the rate of reduction in the perfusate during removal to 30 mM/min or less; (d) limit the perfusion pressure to 20-30 mm Hg, within the practical constraints of the perfusion system; (e) increase the concentration of impermeant in the perfusate to as high as 400 mos/kg, although it is recognized that this departure from plasma-like composition might impose other problems that are not considered in this model. Further, it was observed that the vascular membrane permeability plays a relatively minor role in controlling cellular osmotic injury and vascular perfusion resistance and is therefore not a critical parameter in the perfusion design process.
- Published
- 1998
- Full Text
- View/download PDF
100. Measurement of cell volume loss in the liquid region preceding an advancing phase change interface.
- Author
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Harmison HR, Diller KR, Walsh JR, Neils CM, and Brand JJ
- Subjects
- Freezing, Microscopy methods, Cell Size, Chlorophyta cytology, Chlorophyta physiology, Cryopreservation methods
- Abstract
It is well understood that the solidification of a solution results in a redistribution of solute in the liquid zone. For the freezing of suspensions of cells it is anticipated that accumulation of solute in the region leading a growing ice phase will cause an osmotic response in cells before the ice phase reaches the cells. To measure this phenomenon in a specific algal species, the volume changes in Chlorococcum texanum during freezing were studied using directional solidification cryomicroscopy. The relative cell volume was tracked continuously as a function of temperature and position as cells encountered the moving phase front. The loss of cell volume was measured in the liquid region containing concentrated solute ahead of the growing solid phase.
- Published
- 1998
- Full Text
- View/download PDF
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