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- Nygård, K., et al.
(författare)
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ForMAX – a beamline for multiscale and multimodal structural characterization of hierarchical materials
- 2024
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 31:Pt 2, s. 363-377
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Tidskriftsartikel (refereegranskat)abstract
- The ForMAX beamline at the MAX IV Laboratory provides multiscale and multimodal structural characterization of hierarchical materials in the nanometre to millimetre range by combining small- and wide-angle X-ray scattering with full-field microtomography. The modular design of the beamline is optimized for easy switching between different experimental modalities. The beamline has a special focus on the development of novel fibrous materials from forest resources, but it is also well suited for studies within, for example, food science and biomedical research.
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- Georgantopoulos, Christos K., et al.
(författare)
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Derivation of a qualitative model for the spatial characteristic wavelength of extrusion flow instabilities: Investigation of a polybutadiene rubber through capillary, slit and complex geometry extrusion dies
- 2022
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Ingår i: Macromolecular Materials and Engineering. - : Wiley. - 1439-2054 .- 1438-7492.
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Tidskriftsartikel (refereegranskat)abstract
- The extrusion flow instabilities of a commercial polybutadiene (PBD) are investigated as a function of different extrusion die geometries, such as round capillary, slit, and complex cross-section profile slit dies via capillary rheology. Qualitative models are used to fit the experimental data for the spatial characteristic wavelength (λ) of the appearing extrusion flow instabilities. A new qualitative model for the slit die geometry, rectangular cross-section, is derived based on the theoretical concept of the “two layers” extrudate and the force balance at the die exit region. The proposed qualitative model for the slit die geometry is used to predict the spatial characteristic wavelength (λ) for extrudates obtained by complex cross-section profile slit die geometries similar to industrial manufacturing. Correlation between the ratio of the extensional ( ) and shear ( ) stress at the die exit area and the characteristic dimension, height H for slit dies and diameter D for round capillary dies, is presented. Moreover, a geometry-dependent model is used to predict the spatial characteristic wavelength (λ) of the extrusion flow instabilities from a round capillary die to a slit die and vice versa.
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- Georgantopoulos, Christos K., et al.
(författare)
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Modeling the spatial characteristics of extrusion flow instabilities for styrene-butadiene rubbers: Investigating the influence of molecular weight distribution, molecular architecture, and temperature
- 2021
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Ingår i: Physics of Fluids. - : AIP Publishing. - 1089-7666 .- 1070-6631. ; 33:9
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Tidskriftsartikel (refereegranskat)abstract
- The extrusion flow instabilities of three commercial styrene-butadiene rubbers (SBR) are investigated as a function of molecular weight distribution (MWD); molecular architecture (linear, branched); and temperature. The samples have multimodal MWD, with the main component being SBR and a low amount, less than 10 wt. %, of low-molecular weight hydrocarbons. Deviation from the Cox-Merz rule at high angular frequencies/shear rates becomes intense as the amount of medium-molecular weight component increases. Optical analysis is used to identify and quantify spatial surface distortions, specifically wavelength (λ) and height (h), of the different types of extrusion flow instabilities. Qualitative constitutive models are reviewed and used to fit the experimental data for the spatial characteristics of extrusion flow instability. The fitting parameters as obtained by the models are correlated with molecular properties of the materials. It is found that the characteristic spatial wavelength (λ) increases as the extrusion temperature decreases. Hence, the influence of temperature on the spatial characteristic wavelength is investigated and an Arrhenius behavior is observed.
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- Georgantopoulos, Christos K., et al.
(författare)
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Slip of styrene–butadiene rubbers: The effects of pressure and viscous heating.
- 2024
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Ingår i: Physics of Fluids. - 1089-7666 .- 1070-6631. ; 36:1
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Tidskriftsartikel (refereegranskat)abstract
- During the processing of elastomeric compounds under high flow rates, significant pressure drops (106–108 Pa) are encountered. Under such conditions, the viscosity of these compounds is significantly affected by pressure and viscous heating. Moreover, strong flow rates may cause these systems to slip at the wall, violating the classical no-slip boundary condition of fluid mechanics. To determine the slip velocity by the well-known Mooney method, the effects of pressure and viscous heating should be considered. In this work, an experimental methodology is developed to determine the slip velocity of styrene–butadiene compounds in capillary flow corrected for the effects of pressure and viscous heating. First, the temperature increase due to viscous heating is measured during the extrusion process and accounted for in correcting the experimental data to infer the slip velocity. Consequently, the corrected experimental data for the effects of pressure and viscous heating are used to calculate the slip velocity from the deviation of the linear viscoelastic behavior (deviation from the Cox–Merz rule). The Mooney method is also used to confirm the calculated slip velocity of the elastomeric compounds.
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- Gubanski, Michael, et al.
(författare)
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Randomized phase II study of sequential docetaxel and irinotecan with 5-fluorouracil/folinic acid (leucovorin) in patients with advanced gastric cancer : the GATAC trial
- 2010
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Ingår i: Gastric Cancer. - : Springer Science and Business Media LLC. - 1436-3291 .- 1436-3305. ; 13:3, s. 155-161
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Tidskriftsartikel (refereegranskat)abstract
- Background. The optimal chemotherapy in patients with advanced gastric carcinoma (GC) is yet to be determined. We compared sequential administration of docetaxel and irinotecan, both in combination with infused 5-fluorouracil/leucovorin (5-Fu/Lv), and randomly assigned patients to start with either of the two. Methods. Patients with previously untreated locally advanced or metastatic GC and with measurable lesions (response evaluation criteria in solid tumors; RECIST) were randomly assigned to start with docetaxel 45 m (arm T) or irinotecan 180 mg/m(2) (arm C) with bolus/44-h infusion of 5-Fu/Lv (day 1 every 2 weeks). After four courses, there was a pre-scheduled crossover to the alternative regimen for four additional courses. Results. Eighty-one patients were randomized and 78 started treatment. Complete and partial responses were seen in 31 (40%) patients after 8 weeks and in 32 (41%) after 16 weeks, with similar results in both study arms. The median overall survival (OS) was 11.5 and 10.6 months in arms T and C, respectively (P = 0.3). The two schedules were feasible and did not differ in the overall rate of severe adverse events (SAEs). Conclusion. This is the first randomized comparison of two of the newer cytostatic drugs in GC therapy. No differences favoring either arm T or arm C were found with respect to response rate, OS, or toxicity. The median OS of 11 months indicates that sequential administration of the two combinations is effective and is similar to triple combinations. Thus, comparable efficacy to platinum combinations appears to be obtained with newer, less toxic regimens when given sequentially.
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