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

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1.
  • Woxenius, Johan, 1967-, 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.
2.
  • Franke Stenport, Victoria, 1970-, et al. (författare)
  • Precipitation of calcium phosphate in the presence of albumin on titanium implants with four different possibly bioactive surface preparations. An in vitro study
  • 2008
  • Ingår i: Journal of Materials Science: Materials in Medicine. - 0957-4530. ; 19:12, s. 3497-3505
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the present study was to compare the nucleating behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model with the presence albumin. Titanium discs were blasted (B) and then prepared by alkali and heat treatment (AH), anodic oxidation (AO), fluoridation (F), or hydroxyapatite coating (HA). The discs were immersed in SBF with 4.5 mg/ml albumin for 3 days, 1, 2, 3 and 4 weeks and analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray photoelectron spectroscopy (XPS). Topographic surface characterisation was performed with a contact stylus profilometer. The results demonstrated that the bioactive surfaces initiated an enhanced calcium phosphate (CaP) formation and a more rapid increase of protein content was present on the bioactive surfaces compared to the blasted control surface. The observation was present on all bioactive surfaces. The fact that there was a difference between the bioactive surfaces and the blasted control surface with respect to precipitation of CaP and protein content on the surfaces support the fact that there may be biochemical advantages in vivo by using a bioactive surface.
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3.
  • Johansson, Carina B., 1955-, et al. (författare)
  • Enhanced implant integration with hierarchically structured implants: a pilot study in rabbits
  • 2012
  • Ingår i: Clinical Oral Implants Research. - 1600-0501. ; 23:8
  • Tidskriftsartikel (refereegranskat)abstract
    • AIM: To investigate bone-to-implant bonding for some novel surface modifications with a hierarchic structure and to correlate the in vivo results with surface roughness parameters. MATERIALS AND METHODS: Newly developed implants surfaces were tested in rabbits and compared with the commercially available OsseoSpeed™ (OS) implant. The blasted test samples were subjected to treatment in oxalic acid (AT-II), followed by subsequent etching in hydrofluoric acid (AT-I). Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the surface topography and chemical composition of the implants. Biomechanical testing after 6 weeks of healing was complemented with the quantification of fluorochromes and the results were subjected to a multivariate statistical analysis. RESULTS: The results show, both with biomechanical- and with histomorphometrical tests, that the AT-I implants with different surface roughness at the micro (blasting), submicro (shallow cavities) and nanolevels (precipitates) have a greater bone tissue integration compared with the AT-II- and OS implants. The 2D bone-to-implant contact (BIC) data were in accordance with the 3D removal torque (RTQ) results even if the former were deduced from implants located in spongeous-type bone and the latter in cortical bone. The increase in RTQ values for the test samples AT-I and AT-II compared with the reference complies with the slightly higher S(a) values for these surfaces. CONCLUSIONS: Using a combination of conventional methods with novel quantification of florochrome and multivariate analysis, the influence of surface roughness on different levels could be discriminated. The RTQ and BIC values show that the most hierarchical structure with submicro cavities and nanoscale precipitates possesses the most favourable osseointegration properties.
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4.
  • Svanborg, L. M., et al. (författare)
  • The effect of hydroxyapatite nanocrystals on early bone formation surrounding dental implants.
  • 2011
  • Ingår i: International journal of oral and maxillofacial surgery. - 1399-0020. ; 40:3, s. 308
  • Tidskriftsartikel (refereegranskat)abstract
    • The knowledge of how nanostructures might affect early bone healing and osseointegration is limited. The aim of this study was to investigate if nanometer thick coatings of hydroxyapatite nanocrystals applied on a moderately rough surface might enhance early bone healing on screw-shaped dental implants and to evaluate if the thickness of the coat influences healing. Sandblasted and acid etched titanium implants coated with two different thicknesses of hydroxyapatite (test implants) and sandblasted and acid etched titanium implants (control implants), were inserted in rabbit tibia. After a healing time of 2, 4 and 9 weeks, a removal torque analysis and a histological evaluation were performed. The results from the removal torque analysis showed a tendency for higher values for the double coated hydroxyapatite after 4 weeks and for both the coated surfaces after 9 weeks of healing. The histological evaluations indicated slightly more new bone formation with the coated implants compared with the control; the differences did not reach statistical significance. The present study could not support the importance of nanometer thick coatings of hydroxyapatite nanocrystals in early bone healing, at least not when applied on a blasted and etched surface and placed in a cortical bone.
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5.
  • Galli, Silvia, et al. (författare)
  • Surface Characterization and Clinical Review of Two Commercially Available Implants
  • 2013
  • Ingår i: Implant dentistry. - 1538-2982. ; 22:5
  • Tidskriftsartikel (refereegranskat)abstract
    • PURPOSE: To characterize topographically and chemically the surfaces of 2 commercially available implants. Furthermore, to gather an overview of the clinical results of these implant systems. MATERIALS AND METHODS: Two commercially available oral implants were analyzed using optical interferometry, scanning electron microscopy, and energy dispersive spectroscopy. In addition, a literature search for all the clinical articles on the same implants was performed. RESULTS: No significant differences of topographical parameters were found between the 2 implants, except for the hybrid parameter Sdr presenting significant higher values for the Ankylos implants. Both surfaces had a homogenous microporosity. At higher magnifications of scanning electron microscope images, evenly distributed nanostructures (approximately 10 nm) were visible. Chemically, mainly titanium, oxygen and carbon were detected. Fifty-six clinical articles were included for the review. The implant survival rates (minimum follow-up: 5 years) ranged between 87.7% and 100%. CONCLUSIONS: The examined commercially available implants showed a moderately rough surface, with a homogenous microporosity. Nanofeatures were detected on the surface of both implants. The clinical performances of these implants were comparable to that of other commercialized implant systems.
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6.
  • Dahlström, M, et al. (författare)
  • Impact of polymer surface affinity of novel antifouling agents
  • 2004
  • Ingår i: Biotechnology and Bioengineering. - 1097-0290. ; 86:1, s. 1-8
  • Tidskriftsartikel (refereegranskat)abstract
    • In a previous study we found two agents, the 2-agonist medetomidine ((±)-4-[1-(2,3-dimethylphenyl)ethyl]-1H-imidazole) and the 2-agonist clonidine (2-(2,6-dichloroanilino)-2-imidazoline), that specifically and efficiently impede settlement of the barnacle Balanus improvisus, one of the most serious biofouling organisms in Swedish waters. Medetomidine, but not clonidine, is known to adsorb to solid polystyrene (PS) surfaces in the presence of salt, a feature that is of particular interest in attempts to develop an efficient antifouling surface. We show that medetomidine, but not clonidine, has a significant ability to adsorb to untreated (hydrophobic) PS in two different incubation media: filtered seawater (FSW) and deionized water (mQ). At negatively charged (hydrophilic) PS, medetomidine displays a strong interaction with the surface in both incubation media. At the hydrophilic PS, clonidine also displays a significant interaction with the surface when incubated in mQ and a weaker, but not significant, interaction when incubated in FSW. By studying the effects of time, incubation media, and pH on the adsorption of medetomidine and clonidine, we suggest that medetomidine is associated to hydrophobic PS by means of hydrophobic interactions, while the adsorption of medetomidine and clonidine to hydrophilic PS contains elements of electrostatic interaction. Using time-of-flight secondary ion mass spectroscopy (TOF-SIMS) we detected only weak signals from medetomidine on the hydrophobic PS surfaces, while strong medetomidine signals were observed on hydrophilic PS. This suggests that the adsorbed medetomidine, to a greater extent, desorbed from the hydrophobic rather than from the hydrophilic PS surfaces during exposure to vacuum. The strong surface affinity of medetomidine on both types of surfaces and the preserved antifouling activity are valuable features in designing a marine coating.
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7.
  • 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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8.
  • Göransson, Anna, 1970-, et al. (författare)
  • An in vitro comparison of possibly bioactive titanium implant surfaces.
  • 2009
  • Ingår i: Journal of Biomedical Materials Research Part A. - 1552-4965. ; 88:4, s. 1037-1047
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the study was to compare Ca and P formation (CaP) and subsequent bone cell response of a blasted and four different possibly bioactive commercially pure (cp) titanium surfaces; 1. Fluoride etched (Fluoride), 2. Alkali-heat treated (AH), 3. Magnesium ion incorporated anodized (TiMgO), and 4. Nano HA coated and heat treated (nano HA) in vitro. Furthermore, to evaluate the significance of the SBF formed CaP coat on bone cell response. The surfaces were characterized by Optical Interferometry, Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). CaP formation was evaluated after 12, 24 and 72 h in simulated body fluid (SBF). Primary human mandibular osteoblast-like cells were cultured on the various surfaces subjected to SBF for 72 h. Cellular attachment, differentiation (osteocalcin) and protein production (TGF-beta(1)) was evaluated after 3 h and 10 days respectively. Despite different morphological appearances, the roughness of the differently modified surfaces was similar. The possibly bioactive surfaces gave rise to an earlier CaP formation than the blasted surface, however, after 72 h the blasted surface demonstrated increased CaP formation compared to the possibly bioactive surfaces. Subsequent bone cell attachment was correlated to neither surface roughness nor the amount of formed CaP after SBF treatment. In contrast, osteocalcin and TGF-beta(1) production were largely correlated to the amount of CaP formed on the surfaces. However, bone response (cell attachment, osteocalcin and TGF-F production) on the blasted controls were similar or increased compared to the SBF treated fluoridated, AH and TiMgO surface.
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9.
  • 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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10.
  • 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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