| 1. |
- Breznau, Nate, et al.
(författare)
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Observing many researchers using the same data and hypothesis reveals a hidden universe of uncertainty
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:44
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Tidskriftsartikel (refereegranskat)abstract
- This study explores how researchers analytical choices affect the reliability of scientific findings. Most discussions of reliability problems in science focus on systematic biases. We broaden the lens to emphasize the idiosyncrasy of conscious and unconscious decisions that researchers make during data analysis. We coordinated 161 researchers in 73 research teams and observed their research decisions as they used the same data to independently test the same prominent social science hypothesis: that greater immigration reduces support for social policies among the public. In this typical case of social science research, research teams reported both widely diverging numerical findings and substantive conclusions despite identical start conditions. Researchers expertise, prior beliefs, and expectations barely predict the wide variation in research outcomes. More than 95% of the total variance in numerical results remains unexplained even after qualitative coding of all identifiable decisions in each teams workflow. This reveals a universe of uncertainty that remains hidden when considering a single study in isolation. The idiosyncratic nature of how researchers results and conclusions varied is a previously underappreciated explanation for why many scientific hypotheses remain contested. These results call for greater epistemic humility and clarity in reporting scientific findings.
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| 2. |
- Eichhorst, B., et al.
(författare)
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First-Line Venetoclax Combinations in Chronic Lymphocytic Leukemia.
- 2023
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Ingår i: New England Journal of Medicine. - : MASSACHUSETTS MEDICAL SOC. - 0028-4793 .- 1533-4406. ; 388:19, s. 1739-1754
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Tidskriftsartikel (refereegranskat)abstract
- Background Randomized trials of venetoclax plus anti-CD20 antibodies as first-line treatment in fit patients (i.e., those with a low burden of coexisting conditions) with advanced chronic lymphocytic leukemia (CLL) have been lacking. Methods In a phase 3, open-label trial, we randomly assigned, in a 1:1:1:1 ratio, fit patients with CLL who did not have TP53 aberrations to receive six cycles of chemoimmunotherapy (fludarabine-cyclophosphamide-rituximab or bendamustine-rituximab) or 12 cycles of venetoclax-rituximab, venetoclax-obinutuzumab, or venetoclax-obinutuzumab-ibrutinib. Ibrutinib was discontinued after two consecutive measurements of undetectable minimal residual disease or could be extended. The primary end points were undetectable minimal residual disease (sensitivity,
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| 3. |
- Kattge, Jens, et al.
(författare)
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TRY plant trait database - enhanced coverage and open access
- 2020
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 4. |
- Kazemahvazi, S., et al.
(författare)
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A constitutive model for self-reinforced ductile polymer composites
- 2015
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 71, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- Self-reinforced polymer composites are gaining increasing interest due to their higher ductility compared to traditional glass and carbon fibre composites. Here we consider a class of PET composites comprising woven PET fibres in a PET matrix. While there is a significant literature on the development of these materials and their mechanical properties, little progress has been reported on constitutive models for these composites. Here we report the development of an anisotropic visco-plastic constitutive model for PET composites that captures the measured anisotropy, tension/compression asymmetry and ductility. This model is implemented in a commercial finite element package and shown to capture the measured response of PET composite plates and beams in different orientations to a high degree of accuracy.
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| 5. |
- Khurshid, Mansoor, 1986-, et al.
(författare)
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Residual stress state induced by high frequency mechanical impact treatment in different steel grades – Numerical and experimental study
- 2017
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Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 123, s. 34-42
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Tidskriftsartikel (refereegranskat)abstract
- High frequency mechanical impact treatment is observed to increase the fatigue strength of welded joints. This technique induces compressive residual stresses, increases the local hardness, and reduces the stress concentration by modifying the weld toe radius. The goal of this study was to investigate residual stresses induced by ultrasonic impact treatment in S355, S700MC, and S960 grades steel experimentally and numerically. Plate specimens were manufactured and treated with different treatment intensities i.e. vibration amplitudes of the Sonotrode. The indentation depths were measured by the aid of a laser scanner and residual stresses using X-ray diffraction technique. The effect of steel grade and treatment intensity on the induced compressive residual stress state was firstly studied experimentally. In addition, displacement controlled simulations were carried out to estimate the local residual stress condition considering the effect of different material models. Both the numerically estimated and experimentally measured residual stresses were qualitatively in good agreement. Residual stress state in S355 and S700MC can be estimated well using combined strain rate dependent material model. No significant effect of the treatment intensity is observed on the indentation depth and residual stress state for S355 grade steel. The indentation depth decreases with the increase in the yield strength of the steel.
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| 6. |
- Kühn, Andrea A, et al.
(författare)
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High-frequency stimulation of the subthalamic nucleus suppresses oscillatory beta activity in patients with Parkinson's disease in parallel with improvement in motor performance.
- 2008
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 28:24, s. 6165-73
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Tidskriftsartikel (refereegranskat)abstract
- High-frequency stimulation (HFS) of the subthalamic nucleus (STN) is a well-established therapy for patients with severe Parkinson's disease (PD), but its mechanism of action is unclear. Exaggerated oscillatory synchronization in the beta (13-30 Hz) frequency band has been associated with bradykinesia in patients with PD. Accordingly, we tested the hypothesis that the clinical benefit exerted by STN HFS is accompanied by suppression of local beta activity. To this end, we explored the after effects of STN HFS on the oscillatory local field potential (LFP) activity recorded from the STN immediately after the cessation of HFS in 11 PD patients. Only patients that demonstrated a temporary persistence of clinical benefit after cessation of HFS were analyzed. STN HFS led to a significant reduction in STN LFP beta activity for 12 s after the end of stimulation and a decrease in motor cortical-STN coherence in the beta band over the same time period. The reduction in LFP beta activity correlated with the movement amplitude during a simple motor task, so that a smaller amount of beta activity was associated with better task performance. These features were absent when power in the 5-12 Hz frequency band was considered. Our findings suggest that HFS may act by modulating pathological patterns of synchronized oscillations, specifically by reduction of pathological beta activity in PD.
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| 7. |
- Poulikidou, Sofia, et al.
(författare)
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A material selection approach to evaluate material substitution for minimizing the life cycle environmental impact of vehicles
- 2015
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 83, s. 704-712
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Tidskriftsartikel (refereegranskat)abstract
- Weight reduction is commonly adopted in vehicle design as a means for energy and emissions savings. However, selection of lightweight materials is often focused on performance characteristics, which may lead to sub optimizations of life cycle environmental impact. Therefore systematic material selection processes are needed that integrate weight optimization and environmental life cycle assessment. This paper presents such an approach and its application to design of an automotive component. Materials from the metal, hybrid and polymer families were assessed, along with a novel self-reinforced composite material that is a potential lightweight alternative to non-recyclable composites. It was shown that materials offering the highest weight saving potential offer limited life cycle environmental benefit due to energy demanding manufacturing. Selection of the preferable alternative is not a straightforward process since results may be sensitive to critical but uncertain aspects of the life cycle. Such aspects need to be evaluated to determine the actual benefits of lightweight design and to base material selection on more informed choices.
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| 8. |
- Schneider, Christof, et al.
(författare)
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Bending energy absorption of self-reinforced poly(ethylene terephthalate) composite sandwich beams
- 2016
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Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 140, s. 582-589
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Tidskriftsartikel (refereegranskat)abstract
- Fully recyclable corrugated sandwich beams made from self-reinforced poly(ethylene terephthalate) SrPET are manufactured and tested in quasi-static three-point bending. For a constant areal mass, the influence of mass distribution on peak load and energy absorption is investigated. Beams with a higher proportion of their mass distributed in the core generally show higher peak loads and energy absorption. A finite element (FE) model was developed using an anisotropic visco-plastic constitutive material law. The FE predictions are in excellent agreement with the measurements. When comparing to sandwich beams with similar weight and geometry of different materials, the SrPET sandwich beams outperform corrugated sandwich beams made from aluminium in terms of peak load and energy absorption.
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| 9. |
- Schneider, Christof, et al.
(författare)
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Compression and tensile properties of self-reinforced poly(ethylene terephthalate)-composites
- 2013
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Ingår i: Polymer testing. - : Elsevier. - 0142-9418 .- 1873-2348. ; 32:2, s. 221-230
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Tidskriftsartikel (refereegranskat)abstract
- Tensile and compression properties of self-reinforced poly(ethylene terephthalate) (SrPET) composites has been investigated. SrPET composites or all-polymer composites have improved mechanical properties compared to the bulk polymer but with maintained recyclability. In contrast to traditional carbon/glass fibre reinforced composites, SrPET composites are very ductile, resulting in high failure strains without softening or catastrophic failure. In tension, the SrPET composites behave linear elastically until the fibre-matrix interface fails, at which point the stiffness starts decreasing. As the material is further strained, strain hardening occurs and the specimen finally fails at a global strain above 10%. In compression, the composite initially fails through fibre yielding, and at higher strains through fibre bending. The stress-strain response is reminiscent of an elastic-perfectly plastic material with a high strain to failure (typically over 10%). This indicates that SrPET composites are not only candidates as semi-structural composites but also as highly efficient energy absorbing materials.
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| 10. |
- Schneider, Christof, et al.
(författare)
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Compression properties of novel thermoplastic carbon fibre and poly-ethylene terephthalate fibre composite lattice structures
- 2015
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Ingår i: Materials & Design. - : Elsevier. - 0261-3069. ; 65, s. 1110-1120
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Tidskriftsartikel (refereegranskat)abstract
- A novel manufacturing route to efficiently produce fibre composite lattice structures has been developed. By using thermoplastic composite materials, flat sheets have been continuously folded, cut into a lattice shape and joined into a sandwich structure. Carbon fibre reinforced poly-ethylene terephthalate (CPET) and poly-ethylene terephthalate fibre reinforced poly-ethylene terephthalate (SrPET) materials have been used to explore two different core options; a carbon fibre option which gives high performance but low recyclability and a single polymer PET option which gives lower performance but full recyclability. Parametric numerical simulations have been used to investigate how the various manufacturing parameters affect the mechanical performance of the core. The carbon fibre composite cores have mechanical performance on-par or better than existing metallic and composite lattice cores presented in literature. Single polymer PET cores show better performance compared to high-end foam cores but have considerable lower performance than carbon fibre lattice cores.
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| 11. |
- Schneider, Christof, et al.
(författare)
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Dynamic compression response of self-reinforced poly(ethylene terephthalate) composites and corrugated sandwich cores
- 2015
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 77, s. 96-105
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Tidskriftsartikel (refereegranskat)abstract
- A novel manufacturing route for fully recyclable corrugated sandwich structures made from self-reinforced poly(ethylene terephthalate) SrPET composites is developed. The dynamic compression properties of the SrPET material and the out-of-plane compression properties of the sandwich core structure are investigated over a strain rate range 10(-4)-10(3) s(-1). Although the SrPET material shows limited rate dependence, the corrugated. core structures show significant rate dependence mainly attributed to micro-inertial stabilisation of the core struts and increased plastic tangent stiffness of the SrPE"T material. The corrugated SrPET cores have similar quasi-static performance as commercial polymeric foams but the SrPET cores have superior dynamic compression properties.
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| 12. |
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| 13. |
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| 14. |
- Schneider, Christof, et al.
(författare)
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Impact response of ductile self-reinforced composite corrugated sandwich beams
- 2016
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Ingår i: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 99, s. 121-131
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Tidskriftsartikel (refereegranskat)abstract
- Corrugated sandwich beams made entirely from self-reinforced poly (ethylene terephthalate) SrPET are manufactured and tested dynamically. The beams are subjected to impact loading at the mid-span using a metal foam projectile and the beam deflection is measured. For sandwich beams with a constant areal mass, beams with a high mass portion in the core webs outperform configurations with a high mass portion in the face sheets (given that the face sheets are thick enough to carry the transversal loads induced by the core webs). Reinforcing the face sheet - core web interface further improves the impact response. The strain rate sensitivity of SrPET has also been investigated. A three-dimensional finite element (FE) model has been developed to simulate the impact event and a good agreement is found with the measured response. It is found that corrugated sandwich beams made from SrPET has competitive impact performance compared to similar sandwich beams with equal mass and geometry out of aerospace grade aluminium and carbon fiber/high performance foam sandwich.
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| 15. |
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| 16. |
- Schneider, Christof
(författare)
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Recyclable self-reinforced ductile fiber composite materials for structural applications
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lightweight structures in vehicles are a proven way to reduce fuel consumption and the environmental impact during the use. Lower structural weight can be achieved by using high performance materials such as composites or using the material efficiently as a sandwich structure. Traditional composite materials such as carbon or glass fiber reinforced polymers have high weight specific mechanical properties but are inherently brittle and expensive. They consist of at least two different materials making recycling a difficult endeavor.The best composite material would have good weight specific properties and is ductile, cheap and comprises of a reinforcement and matrix material based on the same recyclable material making recycling easy. In self-reinforced polymer (SrP) composite materials, reinforcing fibers and matrix material are based on the same recyclable thermoplastic polymer making recycling to a straightforward process. SrP composite materials are ductile, inexpensive and have a high energy absorption potential. The aim of this thesis is to investigate the potential of SrP composites in structural applications. Firstly, the quasi-static and dynamic tensile and compression properties of a self-reinforced poly(ethylene terephthalate) (SrPET) composite material are investigated confirming the high energy absorption potential. Sandwich structures out of only SrPET with a lattice core are manufactured and tested in quasi-static out-of-plane compression showing the potential of SrPET as core material. Corrugated sandwich structured out of only SrPET are manufactured and tested in out-of-plane compression over a strain rate range10−4 s−1 - 103 s−1. The corrugated SrPET core has similar quasi-static properties as commercial polymeric foams but superior dynamic compression properties. Corrugated sandwich beams out of only SrPET are manufactured and tested in quasi-static three-point bending confirming the high energy absorption potential of SrPET structures. When comparing the SrPET beams to aluminum beams with identical geometry and weight, the SrPET beams shows higher energy absorption and peak load. The experimental results show excellent agreement with finite element predictions. The impact behaviorof corrugated SrPET sandwich beams during three-point bending is investigated. When comparing SrPET sandwich beams to sandwich beams with carbon fiber face sheets and high performance thermoset polymeric foam with the same areal weight, for the same impact impulse per area, the SrPET shows less mid-span deflection.
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| 17. |
- Sha, Mahesh Kumar, et al.
(författare)
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Validation of methane and carbon monoxide from Sentinel-5 Precursor using TCCON and NDACC-IRWG stations
- 2021
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:9, s. 6249-6304
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Tidskriftsartikel (refereegranskat)abstract
- The Sentinel-5 Precursor (S5P) mission with the TROPOspheric Monitoring Instrument (TROPOMI) on board has been measuring solar radiation backscattered by the Earth's atmosphere and surface since its launch on 13 October 2017. In this paper, we present for the first time the S5P operational methane (CH4) and carbon monoxide (CO) products' validation results covering a period of about 3 years using global Total Carbon Column Observing Network (TCCON) and Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG) network data, accounting for a priori alignment and smoothing uncertainties in the validation, and testing the sensitivity of validation results towards the application of advanced co-location criteria. We found that the S5P standard and bias-corrected CH4 data over land surface for the recommended quality filtering fulfil the mission requirements. The systematic difference of the bias-corrected total column-averaged dry air mole fraction of methane (XCH4) data with respect to TCCON data is -0.26 +/- 0.56 % in comparison to -0.68 +/- 0.74 % for the standard XCH4 data, with a correlation of 0.6 for most stations. The bias shows a seasonal dependence. We found that the S5P CO data over all surfaces for the recommended quality filtering generally fulfil the missions requirements, with a few exceptions, which are mostly due to co-location mismatches and limited availability of data. The systematic difference between the S5P total column-averaged dry air mole fraction of carbon monoxide (XCO) and the TCCON data is on average 9.22 +/- 3.45 % (standard TCCON XCO) and 2.45 +/- 3.38 % (unscaled TCCON XCO). We found that the systematic difference between the S5P CO column and NDACC CO column (excluding two outlier stations) is on average 6.5 +/- 3.54 %. We found a correlation of above 0.9 for most TCCON and NDACC stations. The study shows the high quality of S5P CH4 and CO data by validating the products against reference global TCCON and NDACC stations covering a wide range of latitudinal bands, atmospheric conditions and surface conditions.
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| 18. |
- Velea, Marian Nicolae, et al.
(författare)
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Second order hierarchical sandwich structure made of self-reinforced polymers by means of a continuous folding process
- 2016
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Ingår i: Materials & design. - : Elsevier Ltd. - 0264-1275 .- 1873-4197. ; 102, s. 313-320
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Tidskriftsartikel (refereegranskat)abstract
- One typical way to obtain higher stiffness and strength to weight ratios within structural applications is to use sandwich structures containing lightweight cellular cores. In this study a novel second order hierarchical sandwich structure and its manufacturing principle are described. The whole hierarchical structure is made of a fully recyclable material - different forms of poly-ethylene terephthalate (PET): PET matrix, reinforced with PET fibres (Self reinforced - SrPET) and PET foam resulting in a recyclable structure. The manufacturing path is developed such that it can be implemented within a continuous production line. Out-of-plane compression test are carried out in order to determine the stiffness and strength properties of the proposed structure. An analytical model is developed for evaluating the out-of-plane stiffness and strength properties and used for investigating the influence of the geometric parameters on the structural performance of the proposed hierarchical sandwich structure
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