| 1. |
- Persson, Per, et al.
(author)
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Determination of the detection limit of Ni-59 at the Lund AMS facility by using characteristic projectile X-rays
- 2000
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In: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - 0168-583X. ; 160:4, s. 510-514
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Journal article (peer-reviewed)abstract
- Accelerator mass spectrometry (AMS) is an ultra-sensitive method for counting atoms, both radionuclides and stable nuclides. When using small tandem accelerators to measure heavy isotopes, interfering isobars are often troublesome. One way to reduce this interference is to combine AMS with the detection of characteristic X-rays of the projectile. After analysis in the AMS system it is possible to identify ions of different atomic number by their characteristic X-rays, by slowing down the ions in a suitable target. In this paper, the detection limit of Ni-59 at the Land AMS facility is reported. A method for the chemical extraction of nickel from stainless steel, combined with a purification step to reduce the cobalt content in the sample by several orders of magnitude, is also described. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 2. |
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| 3. |
- Eriksson, Mats, 1963-, et al.
(author)
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Morphology changes of thin Pd films grown on SiO2: influence of adsorbates and temperature
- 1999
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 342:1-2, s. 297-306
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Journal article (peer-reviewed)abstract
- Under certain conditions morphology changes occur when thin Pd films, grown on SiO2 at room temperature, are subject to elevated temperatures. First holes in the metal are observed, followed by network formation and finally isolation of metal islands. This process is known as agglomeration. The influence of gas exposures on this restructuring process has been studied by following variations in the capacitance of the structure and by atomic force microscopy, transmission electron microscopy and ultraviolet photoelectron spectroscopy. The capacitance measurements show that carbonaceous species have an impeding influence on the rate of agglomeration and may lock the film structure in a thermodynamic non-equilibrium state. By removing these species with oxygen exposure, i.e. by forming volatile CO and CO2, a clean surface is obtained and the agglomeration process can proceed. High oxygen or hydrogen coverages also lower the rate of restructuring, compared to the case of a clean surface. For the clean Pd surface, an apparent activation energy of 0.64 eV is found for the restructuring process.
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| 4. |
- Erlandsson, Ragnar, et al.
(author)
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Force interaction between a W tip and Si(111) investigated under ultrahigh vacuum conditions
- 2000
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 62:20, s. 13680-13686
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Journal article (peer-reviewed)abstract
- The force on a W tip has been measured in ultrahigh vacuum during approach and indentation against Si(111). The maximum separation where we detect an attractive force is 5 Å, which is within the range where wave-function overlap should occur. Calculating the van der Waals force using the sphere-flat geometry and a radius of 150 Å that we determine by scanning electron microscopy overestimates the force, while a cone-shaped tip apex is consistent with our results. After contact we observe discontinuous steps in the force curve in agreement with molecular-dynamics simulations. The stiffness of the junction increases during the first 5 Å after contact and stabilizes at ~25 N/m, which is approximately a factor of 3 lower than estimated from classical elasticity theory. The maximum adhesive force is ~5 nN. We also present a model that relates the dynamic behavior of the force-feedback controller to the formation of a connective neck over the tip-surface gap.
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| 5. |
- Erlandsson, Ragnar, et al.
(author)
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Gas-induced restructuring of palladium model catalysts studied with atomic force microscopy
- 1991
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In: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 9:2, s. 825-828
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Journal article (peer-reviewed)abstract
- The structure of thin Pd films evaporated onto planar SiO2 substrates changes dramatically during oxygen/hydrogen exposures in ultrahigh vacuum. In this work we have used an atomic force microscope(AFM), operated in the attractive mode, to obtain the three‐dimensional morphology of the Pd surface for different film thicknesses and treatments, and compared the data with transmission electron microscopy(TEM) micrographs. During restructuring, a 100‐Å film changes from being a smooth continuous film with cracks into metal clusters dispersed on the SiO2 support. In the 5‐Å case the metal films are already well dispersed as fabricated. Here the gas exposure instead results in a clustering effect resulting in larger particles. The AFM gives results which are consistent with TEM micrographs but also gives additional information on metal particle shape which can lead to a further understanding of the restructuring process.
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| 6. |
- Erlandsson, Ragnar, et al.
(author)
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Progress in scanning probe microscopy : High resolution force microscopy and spectroscopy
- 2000
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In: Current Science. - 0011-3891. ; 78:12, s. 1445-1457
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Journal article (peer-reviewed)abstract
- During the last few years the Atomic Force Microscope (AFM) has become capable of routinely obtaining atomic resolution when operated with a vibrating cantilever (ac-mode). Local measurement of the tip-sample force (force spectroscopy) is a powerful tool for investigations of contact phenomena at the atomic scale that are important in fields like friction, tribology, atom manipulation and chemical bond formation. This paper reviews several aspects of the AFM technique such as tip-surface forces, force sensors, operation modes and contrast effects. A study of the Si(111)7 x 7 reconstruction is presented as an example of high resolution AFM imaging.
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| 7. |
- Erlandsson, Ragnar, et al.
(author)
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Scanning force microscopy - examples of applications to surface chemistry
- 1992
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In: Progress in Colloid and Polymer Science. - 0340-255X .- 1437-8027. ; 88, s. 154-161
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Journal article (peer-reviewed)abstract
- Some recent results from the scanning force microscopy activity at our laboratory are presented. A brief description of attractive mode force microscopy is followed by a discussion of the following examples: O2/H2-induced morphology changes in thin palladium films, structure of spin cast polysulfone films, fibrinogen adsorption on hydrophobic SiO2, and force measurements on hydrophobic/hydrophilic substrates.
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| 8. |
- Hultborn, Ragnar, 1946, et al.
(author)
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Ex Vivo Vascular Imaging and Perfusion Studies of Normal Kidney and Tumor Vasculature
- 2024
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In: CANCERS. - 2072-6694. ; 16:10
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Journal article (peer-reviewed)abstract
- Simple Summary Organs as well as cancer require a supply of nutrients and oxygen and removal of waste products. These tasks are carried out by the vascular system. Knowledge of the vascular properties in organs and tumors is key for understanding normal and abnormal function. For cancer, vascular function is also highly relevant to understand response to treatment, metastasis, and tumor progression. In this study, we use various techniques to characterize the vascular tree and flow in kidneys with kidney cancer. We connected kidneys to a perfusion system and used barium sulphate contrast to visualize the vascular architecture contact microangiography. Immunohistochemistry was used to visualize the vessels in relation to perfusion. The vascular resistance was measured using the radioactive microspheres and in cases that were feasible, we used micro-CT to characterize the vascular tree. This work aims to suggest the use of these techniques for any organ or tumor available for ex vivo perfusion.Abstract This work describes a comprehensive study of the vascular tree and perfusion characteristics of normal kidney and renal cell carcinoma. Methods: Nephrectomy specimens were perfused ex-vivo, and the regional blood flow was determined by infusion of radioactive microspheres. The vascular architecture was characterized by micronized barium sulphate infusion. Kidneys were subsequently sagitally sectioned, and autoradiograms were obtained to show the perfusate flow in relation to adjacent contact X-ray angiograms. Vascular resistance in defined tissue compartments was quantified, and finally, the tumor vasculature was 3D reconstructed via the micro-CT technique. Results show that the vascular tree of the kidney could be distinctly defined, and autoradiograms disclosed a high cortical flow. The peripheral resistance unit of the whole perfused specimen was 0.78 +/- 0.40 (n = 26), while that of the renal cortex was 0.17 +/- 0.07 (n = 15 with 114 samples). Micro-CT images from both cortex and medulla defined the vascular architecture. Angiograms from the renal tumors demonstrated a significant vascular heterogeneity within and between different tumors. A dense and irregular capillary network characterized peripheral tumor areas, whereas central parts of the tumors were less vascularized. Despite the dense capillarity, low perfusion through vessels with a diameter below 15 mu m was seen on the autoradiograms. We conclude that micronized barium sulphate infusion may be used to demonstrate the vascular architecture in a complex organ. The vascular resistance was low, with little variation in the cortex of the normal kidney. Tumor tissue showed a considerable vascular structural heterogeneity with low perfusion through the peripheral nutritive capillaries and very poor perfusion of the central tumor, indicating intratumoral pressure exceeding the perfusion pressure. The merits and shortcomings of the various techniques used are discussed.
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| 9. |
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| 10. |
- Kiisk, Madis, et al.
(author)
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The charge state distribution of a carbon beam measured at the lund pelletron accelerator with the newly installed terminal pumping system in use
- 2002
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In: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 481:1-3, s. 1-8
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Journal article (peer-reviewed)abstract
- Charge state distributions for (12) C and C-13 ions have been measured at the Lund Pelletron tandem accelerator for the N-2 gas stripper with a newly installed terminal pumping system in use. A comparison of the results obtained for the ion energies between 1.5 and 2.8 MeV with the foil stripper and the gas stripper without terminal pumping demonstrates the great improvement of the stripping process achieved with the new terminal pumping. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 11. |
- Lin, N, et al.
(author)
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In situ scanning tunneling microscopic and spectroscopic investigation of magnetron-sputtered C and CN thin films
- 2000
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In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:7, s. 4898-4903
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Journal article (peer-reviewed)abstract
- Carbon and carbon nitride films, grown in argon or nitrogen discharges by reactive Jc magnetron sputtering of a graphite target, were characterized by in situ scanning tunneling microscopy. When the growth temperature increased from ambient to 800 degrees C, we observed a topographic evolution of the carbon films from an amorphous to a graphitelike structure, and further to a distorted-graphitic phase with curved and intersecting basal planes, and finally to a surface containing nanotubes and nanodomes. When nitrogen was incorporated into the films, distortion of the graphitic basal planes occurred at a lower temperature compared to the pure carbon case. At temperatures of similar to 200 degrees C and above, regions of a nongraphitic phase, containing a high degree of carbon sp(3) bonds were observed. Spatially resolved tunneling spectroscopic measurements indicated that the band gaps were 0, similar to 0-0.6 eV, and similar to 0.4-2.0 eV for graphitelike structures, the distorted-graphitic phase, and the nongraphitic phase, respectively. Together with ex sial x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy measurements, the results suggest that the incorporation of nitrogen promotes bending of the graphitic basal planes and thereby facilitates the formation of three-dimensional covalently bonded networks with a high degree of sp(3)-coordinated carbon atoms.
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| 12. |
- Lundström, Ingemar, et al.
(author)
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Artificial 'olfactory' images from a chemical sensor using a light-pulse technique
- 1991
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In: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 352:6330, s. 47-50
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Journal article (peer-reviewed)abstract
- THERE is much interest in the use of chemical sensor arrays, in conjunction with pattern-recognition routines, for developing artificial olfactory devices-electronic noses-which can characterize the chemical composition of gas mixtures 1-5. Here we describe a technique that uses a continuous sensing surface and a detection method involving a scanning pulsed light source, to generate images that represent a fingerprint of the gases detected. The detector is a large-area field-effect device with a number of different catalytic metals constituting the detecting surface (the devices active gate) 6,7. A pulsed light beam scanned across this surface generates a photocapacitive current that varies with the value of the surface potential 8,9. A continuous sensing surface of this type provides information that would require an array of hundreds of discrete sensors. The technique also provides a new means of studying the coupling between the electronic properties of catalytic metals and chemical reactions taking place on their surfaces.
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| 13. |
- Olariu, A, et al.
(author)
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Dating of some Romanian fossil bones by combined nuclear methods
- 2002
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In: Journal of Radioanalytical and Nuclear Chemistry. - 0236-5731. ; 253:2, s. 307-311
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Journal article (peer-reviewed)abstract
- A set of fossil bones from Romania has been analysed by accelerator mass spectrometry and by neutron activation analysis in order to estimate their age. The temporal attributing of Malu Rosu archaeological settlement has been extensively analyzed. The radiocarbon age, determined by accelerator mass spectrometry, for this site is 5510+/-200 BP. This is in agreement with the age of 6000+/-2000 BP, obtained by the dating method based on fluorine content, determined by neutron activation analysis.
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| 14. |
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| 15. |
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| 16. |
- Robbie, K, et al.
(author)
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Study of contact formation by high temperature deposition of Ni on SiC
- 2000
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In: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 338-3, s. 981-984
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Journal article (peer-reviewed)abstract
- We report the observation, by scanning tunneling microscopy (STM), scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and atomic force microscopy (AFM), of island formation on SIC during high temperature deposition and annealing of thin Ni films. Ni films with a nominal thickness of 2.5 monolayers were sputter deposited onto H-2-etched single crystal 6H-SiC (0001) substrates heated to 600 degreesC in an ultrahigh vacuum STM system. After the substrates were annealed to 800-1000 degreesC, island formation was observed by STM. The islands were 0.1-0.5 mum in diameter, similar to 30 nm high, and separated by similar to2 mum from each other, with an exceptionally flat top with a peculiar 'stitched' surface structure. A second type of island, similar to1.5 mum in diameter, similar to 10 nm high, and separated by similar to 10 mum from each other, was observed by ex situ AFM and SEM. Microspot AES showed that the first islands are composed of Ni and C, while the second islands are composed of Ni, C, and Si. AES lineshape studies showed that the carbon in both types of islands is graphitically bound as opposed to the carbon in the substrate which is carbidically bound. From comparisons to literature, we believe that the first islands are a new type of graphite intercalation compound. An indexing of Ni on the top graphite sheets is presented for each anneal temperature.
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| 17. |
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| 18. |
- Stenström, Kristina, et al.
(author)
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14C emission from Swedish nuclear power plants and its Eeffect on the 14C levels in the environment
- 2000
-
Reports (other academic/artistic)abstract
- The radionuclide 14C is produced in all types of nuclear reactors mainly by neutron-induced reactions in oxygen (17O), nitrogen (14N) and carbon (13C). Part of the 14C created is continuously released during normal operation as airborne effluents in various chemical forms (such as CO2, CO and hydrocarbons) to the surroundings. Because of the biological importance of carbon and the long physical half-life of 14C, it is of interest to measure the releases and their incorporation into living material. The 14C activity concentrations in annual tree rings and air around two Swedish nuclear power plants (Barsebäck and Forsmark) as well as the background 14C activity levels from two reference sites in southern Sweden during 1973-1996 are presented in this report. In order to verify the reliability of the method some investigations have been conducted at two foreign nuclear sites, Sellafield fuel reprocessing plant in England, and Pickering nuclear generating station in Canada, where the releases of 14C are known to be substantial. Furthermore, results from some measurements in the vicinity of Paldiski submarine training centre in Estonia are presented. The results of the 14C measurements of air, vegetation and annual tree rings around the two Swedish nuclear power plants show very low enhancements of 14C, if at all above the uncertainty of the measurements. Even if the accuracy of the measurements of the annual tree rings is rather good (1-2%) the contribution of 14C from the reactors to the environment is so small that it is difficult to separate it from the prevailing background levels of 14C. This is the case for all sampling procedures: in air and vegetation as well as in annual tree rings. Only on a few occasions an actual increase is observed. However, although the calculations suffer from rather large uncertainties, the calculated release rate from Barsebäck is in fair agreement with reported release data. The results of this investigation show that the effective doses to man related to the releases of 14C from the Swedish light-water reactors at Barsebäck and Forsmark are very low, especially compared to the situation at other nuclear installations, such as the fuel reprocessing plant at Sellafield, England, and the heavy-water reactors at Pickering nuclear generating station, Canada. Lund/Malmö February 2000
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| 19. |
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| 20. |
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| 21. |
- Svedberg, EB, et al.
(author)
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Epitaxial growth of UHV magnetron sputtered Mo thin films on MgO(001) substrates, oxygen segregation and surface reconstructions
- 1999
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In: Surface Science. - 0039-6028 .- 1879-2758. ; 443:1-2, s. 31-43
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Journal article (peer-reviewed)abstract
- Studies of epitaxial growth of Mo thin films on MgO(001) substrates by ultrahigh Vacuum (UHV) d.c. magnetron sputter deposition have shown independently by in situ low energy electron diffraction (LEED), scanning tunnelling microscopy (STM) and time-resolved in situ reflection high-energy electron diffraction (RHEED) measurements that oxygen is present on the Mo surface during the initial stages of growth. Oxygen induced reconstructions are only found for films thinner than similar to 50 nm, and it is shown that the oxygen originates from the MgO substrate. The oxygen is causing the growing film surface to continuously reconstruct with the (root 5 x root 5)R26 degrees 33', p(2 x 2) and c(2 x 2) structures indicating O coverages ranging from similar to 0.8-1.0 ML. STM measurements confirm earlier X-ray diffraction (XRD) and STM measurements of the (root 5 x root 5)R26 degrees 33' reconstruction and show for the first time STM images of the surface structures where p(2 x 2) and c(2 x 2) reconstructions are present. Based on our STM data we suggest surface models for the p(2 x 2) and c(2 x 2) reconstructions. The STM measurements also revealed surfaces randomly interspersed with apparent 2x2 'holes' not visible by techniques such as LEED due to their non-periodic nature. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
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| 22. |
- Yakimov, V, et al.
(author)
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Electrostatic force-feedback force sensor incorporated in an ultrahigh vacuum force microscope
- 2000
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In: Review of Scientific Instruments. - 0034-6748 .- 1089-7623. ; 71:1, s. 133-136
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Journal article (peer-reviewed)abstract
- A force sensor based on a fiber-optic interferometric displacement transducer incorporated in an ultrahigh vacuum atomic force microscope is described. The operation of the sensor is based on balancing the tip-sample interfacial force using an electrostatic actuator. The electrodes of the actuator are formed by the grounded W cantilever and the metallized end facet of the optical fiber used by the interferometer. Chemical reduction of Ag by a wet chemical method is used for metal coating of the fiber end. A special masking procedure is used to obtain a window hole in the metal coating at the position of the fiber core to allow for optical beam output. Using a window instead of a semitransparent metal film allows us to save the low-finesse characteristics of the interferometer which facilitates the calibration of cantilever displacement. The performance of the sensor is discussed and exemplified by experimental results from force-separation measurements on the W-Au system in ultrahigh vacuum. (C) 2000 American Institute of Physics. [S0034-6748(00)01401-5].
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