| 1. |
- Moosmann, Julian, et al.
(författare)
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A load frame for in situ tomography at PETRA III
- 2019
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Ingår i: Developments in X-Ray Tomography XII. - : SPIE. - 0277-786X .- 1996-756X. - 9781510629196 ; 11113
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A load frame for in situ mechanical testing is developed for the microtomography end stations at the imaging beamline P05 and the high-energy material science beamline P07 of PETRA III at DESY, both operated by the Helmholtz- Zentrum Geesthacht. The load frame is fully integrated into the beamline control system and can be controlled via a feedback loop. All relevant parameters (load, displacement, temperature, etc.) are continuously logged. It can be operated in compression or tensile mode applying forces of up to 1 kN and is compatible with all contrast modalities available at IBL and HEMS i.e. conventional attenuation contrast, propagation based phase contrast and differential phase contrast using a grating interferometer. The modularity and flexibility of the load frame allows conducting a wide range of experiments. E.g. compression tests to understand the failure mechanisms in biodegradable implants in rat bone or to investigate the mechanics and kinematics of the tessellated cartilage skeleton of sharks and rays, or tensile tests to illuminate the structure-property relationship in poplar tension wood or to visualize the 3D deformation of the tendonbone insertion. We present recent results from the experiments described including machine-learning driven volume segmentation and digital volume correlation of load tomography sequences.
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| 2. |
- Gerbitz, Armin, et al.
(författare)
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Prevention of CMV/EBV reactivation by double-specific T cells in patients after allogeneic stem cell transplantation : results from the randomized phase I/IIa MULTIVIR-01 study
- 2023
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Ingår i: Frontiers in Immunology. - : Frontiers Media S.A.. - 1664-3224. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionAllogeneic stem cell transplantation is used to cure hematologic malignancies or deficiencies of the hematopoietic system. It is associated with severe immunodeficiency of the host early after transplant and therefore early reactivation of latent herpesviruses such as CMV and EBV within the first 100 days are frequent. Small studies and case series indicated that application of herpes virus specific T cells can control and prevent disease in this patient population.MethodsWe report the results of a randomized controlled multi centre phase I/IIa study (MULTIVIR-01) using a newly developed T cell product with specificity for CMV and EBV derived from the allogeneic stem cell grafts used for transplantation. The study aimed at prevention and preemptive treatment of both viruses in patients after allogeneic stem cell transplantation targeting first infusion on day +30. Primary endpoints were acute transfusion reaction and acute-graft versus-host-disease after infusion of activated T cells.ResultsThirty-three patients were screened and 9 patients were treated with a total of 25 doses of the T cell product. We show that central manufacturing can be achieved successfully under study conditions and the product can be applied without major side effects. Overall survival, transplant related mortality, cumulative incidence of graft versus host disease and number of severe adverse events were not different between treatment and control groups. Expansion of CMV/EBV specific T cells was observed in a fraction of patients, but overall there was no difference in virus reactivation.DiscussionOur study results indicate peptide stimulated epitope specific T cells derived from stem cell grafts can be administered safely for prevention and preemptive treatment of reactivation without evidence for induction of acute graft versus host disease.Clinical trial registrationhttps://clinicaltrials.gov, identifier NCT02227641.
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| 3. |
- Hahn, S., et al.
(författare)
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Spectral transfer from phase to intensity in Fresnel diffraction
- 2016
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Ingår i: PHYSICAL REVIEW A. - : American Physical Society. - 2469-9926. ; 93:5
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Tidskriftsartikel (refereegranskat)abstract
- We analyze theoretically and investigate experimentally the transfer of phase to intensity power spectra of spatial frequencies through free-space Fresnel diffraction. Depending on lambda z (where lambda is the wavelength and z is the free-space propagation distance) and the phase-modulation strength S, we demonstrate that for multiscale and broad phase spectra critical behavior transmutes a quasilinear to a nonlinear diffractogram except for low frequencies. On the contrary, a single-scale and broad phase spectrum induces a critical transition in the diffractogram at low frequencies. In both cases, identifying critical behavior encoded in the intensity power spectra is of fundamental interest because it exhibits the limits of perturbative power counting but also guides resolution and contrast optimization in propagation-based, single-distance, phase-contrast imaging, given certain dose and coherence constraints.
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| 4. |
- Moosmann, Julian, et al.
(författare)
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Biodegradable magnesium-based implants in bone studied by synchrotron radiation microtomography
- 2017
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Ingår i: Developments in X-Ray Tomography XI. - : SPIE - International Society for Optical Engineering. ; 10391
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Konferensbidrag (refereegranskat)abstract
- Permanent implants made of titanium or its alloys are the gold standard in many orthopedic and traumatological applications due to their good biocompatibility and mechanical properties. However, a second surgical intervention is required for this kind of implants as they have to be removed in the case of children that are still growing or on patient's demand. Therefore, magnesium-based implants are considered for medical applications as they are degraded under physiological conditions. The major challenge is tailoring the degradation in a manner that is suitable for a biological environment and such that stabilization of the bone is provided for a controlled period. In order to understand failure mechanisms of magnesium-based implants in orthopedic applications and, further, to better understand the osseointegration, screw implants in bone are studied under mechanical load by means of a push-out device installed at the imaging beamline P05 of PETRA III at DESY. Conventional absorption contrast microtomography and phasecontrast techniques are applied in order to monitor the bone-to-implant interface under increasing load conditions. In this proof-of-concept study, first results from an in situ push-out experiment are presented.
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| 5. |
- Peruzzi, Niccolò, et al.
(författare)
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Multimodal ex vivo methods reveal that Gd-rich corrosion byproducts remain at the implant site of biodegradable Mg-Gd screws
- 2021
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Ingår i: Acta Biomaterialia. - : Elsevier. - 1742-7061 .- 1878-7568. ; 136, s. 582-591
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Tidskriftsartikel (refereegranskat)abstract
- Extensive research is being conducted on magnesium (Mg) alloys for bone implant manufacturing, due to their biocompatibility, biodegradability and mechanical properties. Gadolinium (Gd) is among the most promising alloying elements for property control in Mg alloy implants; however, its toxicity is controversial. Investigating Gd behavior during implant corrosion is thus of utmost importance. In this study, we analyzed the degradation byproducts at the implant site of biodegradable Mg-5Gd and Mg-10Gd implants after 12 weeks healing time, using a combination of different imaging techniques: histology, energy-dispersive x-ray spectroscopy (EDX), x-ray microcomputed tomography (µCT) and neutron µCT. The main finding has been that, at the healing time in exam, the corrosion appears to have involved only the Mg component, which has been substituted by calcium and phosphorus, while the Gd remains localized at the implant site. This was observed in 2D by means of EDX maps and extended to 3D with a novel application of neutron tomography. X-ray fluorescence analysis of the main excretory organs also did not reveal any measurable accumulation of Gd, further reinforcing the conclusion that very limited or no removal at all of Gd-alloy happened during degradation.
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| 6. |
- Wallmeier, Malte, et al.
(författare)
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Phenomenological analysis of constrained in-plane compression of paperboard using micro-computed tomography Imaging
- 2021
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Ingår i: Nordic Pulp & Paper Research Journal. - : De Gruyter Open Ltd. - 0283-2631 .- 2000-0669. ; 36:3, s. 491-
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Tidskriftsartikel (refereegranskat)abstract
- Large deformations under in-plane compression of paperboard appear in forming processes like hydroforming, pressforming and deep drawing, but the mechanisms of deformation have not been studied on a micromechanical level. A constrained in-plane compression test is presented. This test allows for in-plane compression, buckling, wrinkling and compaction. The constrained compression test is realized using a DEBEN CT-500 in-situ tester for laboratory microtomography and synchrotron microtomography. Experiments with five different materials spanning from laboratory handsheets to commercially available multi-layered paperboards are performed. Image processing is used to observe the local out-of-plane fiber orientation and compaction. A phenomenological investigation of the deformation behavior of these materials is presented. Delamination is found to be the primary mechanisms of failure in the multi-layered boards. Furthermore, a porous network structure, created by using long and minimally refined softwood fibers, is found to facilitate the formation of uniform wrinkles and compaction.
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| 7. |
- Willumeit-Roemer, Regine, et al.
(författare)
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The Comparability of In Vitro and In Vivo Experiments for Degradable Mg Implants
- 2022
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Ingår i: MAGNESIUM TECHNOLOGY 2022. - Cham : Springer. - 9783030925338 - 9783030925321 ; , s. 8-15
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Konferensbidrag (refereegranskat)abstract
- Mg implants possess a great potential for clinical applications. Thousands of patients are already successfully treated with Mg implants and the number of approved products increases. Despite the fact that the implants generally work, we know that we have not yet reached a full understanding of all processes which occur during the degradation of the material and tissue regeneration. A prerequisite for a comprehensive description is the visualization and analysis of the in vivo processes with high resolution, while avoiding metal artefacts during imaging and taking care of different imaging properties of inorganic and organic matrices. Here, synchrotron radiation-based micro-computed tomography was utilized to determine the degradation rates for two implant materials (Mg-5Gd and Mg-10Gd, wt. %) in vitro and in vivo. The comparison for in vitro and in vivo degradation in terms of degradation rate and pitting factor shows that in vitro experiments predict in vivo results the error. As a second aspect, push-out experiments revealed a better integration into bone for Mg-10Gd and the improvement of implant stability over time. Finally, micro X-ray fluorescence spectrometry was applied to determine the elemental composition of degradation products around the Mg-5Gd specimen in vivo. This technique shows that the Mg content of the degrading specimen is decreasing while the Gd content stays constant.
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| 8. |
- Willumeit-Römer, Regine, et al.
(författare)
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Visualization of Implant Failure by Synchrotron Tomography
- 2018
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Ingår i: TMS 2018 147th Annual Meeting & Exhibition Supplemental Proceedings. - Cham : Springer. - 9783319725253 - 9783319725260 ; , s. 275-284
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Konferensbidrag (refereegranskat)abstract
- Magnesium (Mg) and its alloys degrade under physiological conditions. But how strong is the connection between the implant, the corrosion layer and the surrounding tissue, namely bone? Biomechanical tests like push-out tests have shown that a degraded Mg-pin is surprisingly well integrated with the bone “as reported by Castellani et al. (Acta Biomater 7(1):432–440, 2011) [1]”. High-resolution synchrotron tomography offers a deep look into the microstructure of the material as well as of the bone during deformation until fracture happens. Here we present first data from an in situ tomography experiment of a biodegradable Mg-based implant under compressive load showing how Mg implants are incorporated into bone.
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