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Sökning: swepub > Malmö högskola > Engelska > Göteborgs universitet > Chalmers tekniska högskola

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2.
  • Woxenius, Johan, et al. (författare)
  • Utilising more of the loading space in intermodal line trains – measures and decision support
  • 2013
  • Ingår i: Computers in industry. - 0166-3615. ; 64:2, s. 146-154
  • Tidskriftsartikel (refereegranskat)abstract
    • The focus of this article is to identify, characterise and qualitatively evaluate the existing measures for increasing the utilisation of loading space in intermodal road–rail freight line trains. Normally, these trains operate like intercity passenger trains, because they make short unit load transhipment stops along rail corridors in order to travel comparatively small and short flows. The measures for loading space utilisation include adapting the train’s capacity, changing the departure times, altering the train routes and sending trucks to different terminals as well as replacing rail transport with trucks. Some of the measures require improved information sharing, and executives can strengthen the effect of the measures by adding decision support systems and price incentives to transport buyers.
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4.
  • Fröjd, Victoria, et al. (författare)
  • In situ analysis of multispecies biofilm formation on customized titanium surfaces.
  • 2011
  • Ingår i: Molecular oral microbiology. - 2041-1014. ; 26:4, s. 241-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Many studies to identify surfaces that enhance the incorporation of dental implants into bone and soft-tissue have been undertaken previously. However, to succeed in the clinical situation, an implant surface must not support development of microbial biofilms with a pathogenic potential. As a first step in investigating this, we used two-species and three-species biofilm models with 16S ribosomal RNA fluorescence in situ hybridization and confocal laser scanning microscopy to examine the effect of surface characteristics on biofilm formation by species that can colonize titanium implants in vivo: Streptococcus sanguinis, Actinomyces naeslundii and Lactobacillus salivarius. Surfaces blasted with Al(2) O(3) (S(a) = 1.0-2.0 μm) showed a seven-fold higher bacterial adhesion after 2 h than turned surfaces (S(a) = 0.18 μm) whereas porous surfaces, generated by anodic oxidation (S(a) = 0.4 μm), showed four-fold greater adhesion than turned surfaces. Hence, increased roughness promoted adhesion, most likely through protection of bacteria from shear forces. Chemical modification of the blasted and oxidized surfaces by incorporation of Ca(2+) ions reduced adhesion compared with the corresponding non-modified surfaces. After 14 h, biofilm growth occurred in the three-species model but not in the two-species consortium (containing S. sanguinis and A. naeslundii only). The biofilm biovolume on all surfaces was similar, suggesting that the influence of surface characteristics on adhesion was compensated for by biofilm development.
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5.
  • Jimbo, Ryo, et al. (författare)
  • Histological and three-dimensional evaluation of osseointegration to nanostructured calcium phosphate-coated implants.
  • 2011
  • Ingår i: Acta biomaterialia. - 1878-7568.
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanostructures on implant surfaces have been shown to enhance osseointegration; however, commonly used evaluation techniques are probably not sufficiently sensitive to fully determine the effects of this process. This study aimed to observe the osseointegration properties of nanostructured calcium phosphate (CaP)-coated implants, by using a combination of three-dimensional imaging and conventional histology. Titanium implants were coated with stable CaP nanoparticles using an immersion technique followed by heat treatment. Uncoated implants were used as the control. After topographical and chemical characterizations, implants were inserted into the rabbit femur. After 2 and 4weeks, the samples were retrieved for micro-computed tomography and histomorphometric evaluation. Scanning electron microscopy evaluation indicated that the implant surface was modified at the nanoscale by CaP to obtain surface textured with rod-shaped structures. Relative to the control, the bone-to-implant contact for the CaP-coated implant was significantly higher at 4weeks after the implant surgery. Further, corresponding 3-D images showed active bone formation surrounding the implant. 3-D quantification and 2-D histology demonstrated statistical correlation; moreover, 3-D quantification indicated a statistical decrease in bone density in the non-coated control implant group between 2 and 4weeks after the surgery. The application of 3-D evaluation further clarified the temporal characteristics and biological reaction of implants in bone.
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6.
  • Meirelles, Luiz, et al. (författare)
  • Bone reaction to nano hydroxyapatite modified titanium implants placed in a gap-healing model
  • 2008
  • Ingår i: Journal Biomedical MAterials Research - A. - 1549-3296. ; 87:3, s. 624-631
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanohydroxyapatite materials show similar chemistry to the bone apatite and depending on the underlying topography and the method of preparation, the nanohydroxyapatite may simulate the specific arrangement of the crystals in bone. Hydroxyapatite (HA) and other CaP materials have been indicated in cases in which the optimal surgical fit is not achievable during surgery, and the HA surface properties may enhance bone filling of the defect area. In this study, very smooth electropolished titanium implants were used as substrata for nano-HA surface modification and as control. One of each implant (control and nano HA) was placed in the rabbit tibia in a surgical site 0.7 mm wider than the implant diameter, resulting in a gap of 0.35 mm on each implant side. Implant stability was ensured by a fixating plate fastened with two side screws. Topographical evaluation performed with an optical interferometer revealed the absence of microstructures on both implants and higher resolution evaluation with AFM showed similar nanoroughness parameters. Surface pores detected on the AFM measurements had similar diameter, depth, and surface porosity (%). Histological evaluation demonstrated similar bone formation for the nano HA and electropolished implants after 4 weeks of healing. These results do not support that nano-HA chemistry and nanotopography will enhance bone formation when placed in a gap-healing model. The very smooth surface may have prevented optimal activity of the material and future studies may evaluate the synergic effects of the surface chemistry, micro, and nanotopography, establishing the optimal parameters for each of them.
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7.
  • Meirelles, Luiz, et al. (författare)
  • Nano hydroxyapatite structures influence early bone formation
  • 2008
  • Ingår i: Journal Biomedical Materials Research - A. - 1549-3296. ; 87:2, s. 299-307
  • Tidskriftsartikel (refereegranskat)abstract
    • In a study model that aims to evaluate the effect of nanotopography on bone formation, micrometer structures known to alter bone formation, should be removed. Electropolished titanium implants were prepared to obtain a surface topography in the absence of micro structures, thereafter the implants were divided in two groups. The test group was modified with nanosize hydroxyapatite particles; the other group was left uncoated and served as control for the experiment. Topographical evaluation demonstrated increased nanoroughness parameters for the nano-HA implant and higher surface porosity compared to the control implant. The detected features had increased size and diameter equivalent to the nano-HA crystals present in the solution and the relative frequency of the feature size and diameter was very similar. Furthermore, feature density per microm(2) showed a decrease of 13.5% on the nano-HA implant. Chemical characterization revealed calcium and phosphorous ions on the modified implants, whereas the control implants consisted of pure titanium oxide. Histological evaluation demonstrated significantly increased bone formation to the coated (p < 0.05) compared to uncoated implants after 4 weeks of healing. These findings indicate for the first time that early bone formation is dependent on the nanosize hydroxyapatite features, but we are unaware if we see an isolated effect of the chemistry or of the nanotopography or a combination of both.
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8.
  • Svanborg Melin, Lory, et al. (författare)
  • Surface characterization of commercial oral implants on the nanometer level.
  • 2010
  • Ingår i: Journal of biomedical materials research. Part B, Applied biomaterials. - 1552-4981. ; 92B:2, s. 462-469
  • Tidskriftsartikel (refereegranskat)abstract
    • Lately, there has been a growing interest in how the presence of nanometer structures on a bone integrated implant surface influences the healing process. Recent in vitro studies have revealed an increased osteoblast response to different nanophase surfaces. Some commercial implant brands claim their implants have nanometer structures. However, at present, there are no studies where the nano topography of today's commercially available oral implants has been investigated. The aim of this study was to characterize commercial oral implants on the nanometer level and to investigate whether or not the nanometer surface roughness was correlated to the more well-known micrometer roughness on the implants. Twelve different commercial screw-shaped oral implants with various surface modifications were examined using scanning electron microscopy and a white light interferometer. The interferometer is suitable for detection of nanoscale roughness in the vertical dimension; however, limitation exists on the horizontal due to the wavelength of the light. A 1 x 1 microm Gaussian filter was found to be useful for identifying nm roughness with respect to height deviation. The results demonstrated that an implant that was smooth on the micrometer level was not necessarily smooth on the nanometer level. Different structures in the nanometer scale was found on some of the implants, indicating that to fully understand the relationship between the properties of an implant surface and its osseointegration behavior, a characterization at the nanometer scale might be relevant.
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9.
  • Westas, Emma, et al. (författare)
  • Using QCM-D to study the adhesion of human gingival fibroblasts on implant surfaces
  • 2015
  • Ingår i: Journal of Biomedical Materials Research. Part A. - 1549-3296. ; 103:10, s. 3139-3147
  • Tidskriftsartikel (refereegranskat)abstract
    • Sealing the soft tissue-implant interface is one of the key issues in preventing transcutaneous implant-associated infections. A promising surface modification for improving osseointegration and possibly soft tissue integration is to coat the implant surface with hydroxyapatite (HA) nanoparticles. When new implant materials are developed, their ability to facilitate cell attachment and spreading are commonly investigated in vitro to establish their potential for good in vivo performance. However, commonly used techniques, such as microscopy methods, are time consuming, invasive, and subjective. This is the first study using quartz crystal microbalance with dissipation monitoring, where the real-time adhesion of biopsy-derived human gingival fibroblasts onto titanium and nanostructured HA was investigated. Experiments were performed for at least 16 h, and we found that cellular attachment and spreading kinetics can be followed in situ by observing the change in dissipation and frequency with time. Interestingly, a correlation between cell coverage and the magnitude of dissipation shift reached at the end of the experiment was found, but no such trend was observed for the frequency. Furthermore, the level of cell coverage was found to influence the cellular attachment and spreading behavior. No difference in cell response to the two surface types, Ti and nanostructured HA, was found. (c) 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3139-3147, 2015.
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10.
  • Bougas, Kostas, et al. (författare)
  • In vitro Evaluation of Calcium Phosphate Precipitation on Possibly Bioactive Titanium Surfaces in the Presence of Laminin.
  • 2011
  • Ingår i: Journal of Oral & Maxillofacial Research. - 2029-283X. ; 2:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives: The aim of the present study was to evaluate calcium phosphate precipitation and the amount of precipitated protein on three potentially bioactive surfaces when adding laminin in simulated body fluid. Material and Methods: Blasted titanium discs were prepared by three different techniques claimed to provide bioactivity: alkali and heat treatment (AH), anodic oxidation (AO) or hydroxyapatite coating (HA). A blasted surface incubated in laminin-containing simulated body fuid served as a positive control (B) while a blasted surface incubated in non laminin-containing simulated body fuid served as a negative control (B-). The immersion time was 1 hour, 24 hours, 72 hours and 1 week. Surface topography was investigated by interferometry and morphology by Scanning Electron Microscopy (SEM). Analysis of the precipitated calcium and phosphorous was performed by Energy Dispersive X-ray Spectroscopy (EDX) and the adsorbed laminin was quantified by iodine (125I) labeling. Results: SEM demonstrated that all specimens except for the negative control were totally covered with calcium phosphate (CaP) after 1 week. EDX revealed that B- demonstrated lower sum of Ca and P levels compared to the other groups after 1 week. Iodine labeling demonstrated that laminin precipitated in a similar manner on the possibly bioactive surfaces as on the positive control surface. Conclusions: Our results indicate that laminin precipitates equally on all tested titanium surfaces and may function as a nucleation center thus locally elevating the calcium concentration. Nevertheless further studies are required to clarify the role of laminin in the interaction of biomaterials with the host bone tissue.
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