| 1. |
- Allard, Erik, et al.
(författare)
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Comparing capillary electrophoresis : mass spectrometry fingerprints of urine samples obtained after intake of coffee, tea, or water.
- 2008
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 80:23, s. 8946-8955
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Tidskriftsartikel (refereegranskat)abstract
- Metabolomic fingerprinting is a growing strategy for characterizing complex biological samples without detailed prior knowledge about the metabolic system. A two-way analysis system with liquid separation and mass spectrometric detection provides detail-rich data suitable for such fingerprints. As a model study, human urine samples, obtained after intake of coffee, tea, or water, were analyzed with capillary electrophoresis electrospray ionization time-of-flight mass spectrometry (CE−ESI-TOF-MS). In-house-developed software (in Matlab) was utilized to manage and explore the large amount of data acquired (230 CE−MS runs, each with 50−100 million nonzero data points). After baseline and noise reduction, followed by suitable binning in time and m/z, the data sets comprised 9 and 14 million data points in negative and positive ESI mode, respectively. Finally, a signal threshold was applied, further reducing the number to about 100 000 data points per data set. A set of interactive exploratory tools, utilizing principal component analysis (PCA) and analysis of variance (ANOVA) results based on a general linear model, facilitated visual interpretation with score plots (for group assessment) and differential fingerprints (for “hot spot” detection). In the model study highly significant differences due to beverage intake were obtained among the 10 first principal components (p < 10−6 for two of the components in both ESI modes). Especially, the contrasts between “coffee” and “tea or water” indicated several “hot spots” with highly elevated intensities (e.g., for uncharged masses 93, 94, 109, 119, 123, 132, 148, 169, 178, 187, 190, and 193) suitable for further analysis, for example, with tandem MS.
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| 2. |
- Almqvist, Bjarne, et al.
(författare)
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Magnetic characterisation of magnetite and hematite from the Blötberget apatite-iron-oxide deposits (Bergslagen), south-central Sweden
- 2019
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Ingår i: Canadian journal of earth sciences (Print). - : Canadian Science Publishing. - 0008-4077 .- 1480-3313. ; 56:9, s. 948-957
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Tidskriftsartikel (refereegranskat)abstract
- Rock magnetic measurements were carried out on drill core material and hand specimens from the Blötberget apatite-iron oxide deposit in the Bergslagen ore province, south-central Sweden, to characterise their magnetic properties. Measurements included several kinds of magnetic susceptibility and hysteresis parameters. Petrographic and scanning electron microscopy (SEM) were used to independently identify and quantify the amount and type of magnetite and hematite. Two hematite-rich samples were studied with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify the trace element chemistry in hematite and investigate the potential influence of trace elements on magnetic properties. Three aspects of this study are noteworthy. 1) Hematite-rich samples display strong anisotropy of magnetic susceptibility, which is likely to affect the appearance and modelling of magnetic anomalies. 2) The magnitude-drop in susceptibility across Curie and Néel temperature transitions show significant correlation with the respective weight percent (wt%) of magnetite and hematite. Temperature dependent magnetic susceptibility measurements can therefore be used to infer the amounts of both magnetite and hematite. 3) observations of a strongly depressed Morin transition at ca -60 to -70 C (200 to 210 K) are made during low-temperature susceptibility measurements. This anomalous Morin transition is most likely related to trace amounts of V and Ti that substitute for Fe in the hematite. When taken together, these magnetic observations improve the understanding of the magnetic anomaly signature of the Blötberget apatite-iron oxide deposits and may potentially be utilised in a broader context when assessing similar (Paleoproterozoic) apatite-iron oxide systems.
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| 3. |
- Bergman, Daniel, et al.
(författare)
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Pre-existing canine anti-IgG antibodies: implications for immunotherapy, immunogenicity testing and immunoassay analysis
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- One of the most enigmatic features of humoral immunity is the prevalent presence of circulating autoantibodies against IgG. These autoantibodies consist of several subsets, including rheumatoid factors, anti-Fab/anti-F(ab′)2-autoantibodies, and anti-idiotypic antibodies. Anti-IgG autoantibodies can impair the safety and efficacy of therapeutic antibodies and interfere with immunogenicity tests in clinical trials. They can also cross-react with allospecific IgG, presenting as heterophilic antibodies that interfere with diagnostic immunoassays. Owing to these factors, recent years have seen a resurgent interest in anti-IgG autoantibodies, but their underlying clinical significance, as well as biological roles and origins, remain opaque. Increased knowledge about canine anti-IgG autoantibodies could facilitate the development of canine immunotherapies and help in understanding and counteracting immunoassay interference. This study investigated the clinical significance and interconnection of heterophilic antibodies, anti-Fab, and anti-F(ab′)2-autoantibodies in dogs. We performed a 2-year prospective follow-up of dogs with heterophilic antibodies and analyzed serum for anti-Fab and anti-F(ab′)2-autoantibodies. Canine heterophilic antibodies can persist for at least 2 years in serum. A widespread occurrence of anti-Fab and anti-F(ab′)2-autoantibodies was found, with reactivity to cryptic epitopes in the IgG hinge region and sporadic cross-reactivity with mouse IgG. Canine anti-Fab and anti-F(ab′)2-autoantibodies are thus potential sources of clinical immunogenicity and immunoassay interference.
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| 4. |
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| 6. |
- Bäckström, Daniel, 1985
(författare)
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Experimental and modelling studies of particle radiation in flames
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of solid fuels is an important part of many industrial and power generation processes. The global use of coal in these processes is vast and thus also the related emissions of CO2 to the atmosphere. It is not possible to continue on the path with continuously increasing emissions of CO2 if the global climate targets should be met. Two strategies to reduce the emissions from large scale coal combustion is to apply oxy-fuel combustion, which is one of the proposed Carbon Capture and Storage (CCS) technologies, or to switch fuel from coal to biomass. Solid fuels are often combusted in pulverized form in flames, where radiation is the most important heat transfer mechanism. When firing solid fuels particle radiation is the dominating contributor to the radiative heat transfer. Application of either oxy-fuel combustion or fuel-switching in combustion processes will change the radiative conditions in the combustion chamber, which implies that knowledge about the main heat transfer mechanism is needed when designing or retrofitting furnaces for the new conditions. The aim with this work is to develop a methodology combining measurements and modelling to quantify the radiative heat transfer in flames, with a special emphasis on the particle radiation features. Parameters, which are of particular importance in flame combustion such as particle temperature, particle type and size distribution have been measured, and the influence on the flame radiation has been analyzed using a detailed radiation model. The experimental work was performed in Chalmers 100 kWfuel oxy-fuel test unit and in a 400 kWfuel scale model of a rotary kiln furnace. In the 400 kW unit the influence on flame radiation of co-firing of coal and biomass was studied. The radiative intensity, measured with a narrow angle radiometer, has been used as reference data in all studies. An optical FTIR based system for measurement of the in-flame spectral radiation was tested and a system for extraction of particles from the flames was developed in this work. The particle size distribution and particle type were investigated using a low-pressure impactor and a scanning mobility particle sizer (SMPS). Detailed models describing the gas and particle properties were applied in the modelling work: a statistical narrow band model for the gas properties and Mie- or Rayleigh theory for the particle properties. In all investigated solid fuel flames, particles were found to dominate the radiation. In the investigated lignite flame in the Chalmers unit, char particles were found to be the main contributor with only a small influence of soot. In an analysis of spectrally resolved particle radiation, the temperature of the char particles was estimated to be approximately 200°C lower than the gas temperature in a position corresponding to peak temperature conditions of the flame. The soot volume fraction in a sooting air fired propane flame was determined to be 6E-8 based on measurements with the SMPS instrument, and this concentration resulted in a good agreement between modelled and measured intensity. The results from the 400 kW study showed that it is possible to obtain similar radiation intensity in the co-firing flames as in the coal flames. But, the length of the radiating part of the flames was shorter for the co-firing flames. Radiation measurements in flames of two almost identical coal types for similar combustion conditions revealed a significant difference in the radiative intensity. This result shows the difficulty of predicting flame radiation without performing measurements, since the radiation depends on factors such as soot formation, which is highly dependent on fuel and combustion conditions.
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| 7. |
- Bäckström, Daniel, 1985
(författare)
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Experimental and modelling studies of radiative heat transfer in flames
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Combustion of solid fuels is used extensively for electricity generation purposes. However, combustion of fossil fuels leads to CO2 emissions which enhance the greenhouse gas effect. Carbon capture and storage (CCS) is a proposed solution where the CO2 is captured and stored instead of being emitted to the atmosphere. One of the main CCS technologies considered is oxy-fuel combustion. In the present work, the radiative heat transfer occurring in both air-fuel and oxy-fuel atmospheres are investigated.The most common technique for combustion of solid fuels is pulverized coal combustion. Coal is milled and fed to the furnace in a number of burners where the coal is combusted. In the furnace radiative heat transfer is the dominating heat transfer mechanism and both particles and gases contribute to this heat transfer. In oxy-fuel combustion, the air is replaced by oxygen and recirculated flue gases, providing a N2-free flue gas. This changes the radiative properties of the gas and enables flexible operation of the furnaces which requires a fundamental understanding of the heat transfer in the combustion chamber. This work is therefore focused on radiative heat transfer with special emphasis on particle radiation which is an important topic both in air- and oxy-fuel flames. This work combines experimental work and modelling with the aim to discuss and answer important questions related to radiation in coal and gas-fired flames. The two topics in focus are particle radiation and Turbulence-Radiation Interaction. The experimental work has been performed in the Chalmers 100 kW oxy-fuel test unit. A new methodology has been developed to study the particle radiation in coal flames. The method consists of a combination of experimental and modelling work. The experiments include measurements of spectrally resolved radiation, total radiative intensity, gas temperature and gas composition. The spectrally resolved radiation was measured with an FTIR-based probe technique which provides simultaneous estimation of the particle temperature and the amount of particles present in the flame. The radiation modelling is based on particle properties from the Mie-theory and a Statistical Narrow-Band model for the gas properties. The radiative intensity was calculated and finally compared with the measured total radiative intensity with a Narrow Angle Radiometer. The modelled and measured intensity agrees well, which demonstrates the potential of the methodology. The methodology also makes it possible to estimate the soot volume fraction and the contribution from soot to the total particle radiation. The results showed that the soot volume fraction in the centre position of the investigated flame is approximately 1e-7 and that the soot contributes with maximum 40% of the total particle radiation. The Turbulence-Radiation Interactions was evaluated with a simplified model where the temperature fluctuations were measured with the FTIR-based system. The investigation was carried out in two oxy-fuel and one air-fired propane flame. Fluctuations in gas temperature of up to 400 K were seen, but the influence from these fluctuations on the radiative heat transfer was negligible. The temperature fluctuations observed in both the air-fired and the oxy-fuel flames were in the same order of magnitude
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| 8. |
- Bäckström, Daniel, 1985, et al.
(författare)
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Gas temperature and radiative heat transfer in oxy-fuel flames
- 2012
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Ingår i: The 37th International Technical Conference on Clean Coal & Fuel Systems, Clearwater USA, 3-7/6-2012. - 9780932066374
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents measurements of the gas temperature, including fluctuations, and its influence on the radiative heat transfer in oxy-fuel flames. The measurements were carried out in the Chalmers 100 kW oxy-fuel test unit. The in-furnace gas temperature was measured by a suction pyrometer and by an optical system based on FTIR-spectroscopy. The radiation intensity was measured by a Narrow Angle Radiometer and the gas radiation was calculated with a Statistical Narrow Band model. The overall agreement between the two temperature measurement techniques was good. The optical system showed a lower temperature than the suction pyrometer in the low velocity regions of the furnace, a difference which is likely to be an effect of the purge gas added in the optical probe. The measured temperature fluctuations were evaluated by modeling of the gas radiation. The influence from the measured fluctuations on the radiative heat transfer shows no effect of turbulence-radiation interaction. However, by comparing with temperature fluctuations in other flames it can be seen that the fluctuations measured here are relatively small. Further research is needed to clarify to which extent the applied methods can account for the turbulence-radiation interaction in the investigated flame.
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| 9. |
- Bäckström, Daniel, 1973-
(författare)
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Managing and Exploring Large Data Sets Generated by Liquid Separation - Mass Spectrometry
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A trend in natural science and especially in analytical chemistry is the increasing need for analysis of a large number of complex samples with low analyte concentrations. Biological samples (urine, blood, plasma, cerebral spinal fluid, tissue etc.) are often suitable for analysis with liquid separation mass spectrometry (LS-MS), resulting in two-way data tables (time vs. m/z). Such biological 'fingerprints' taken for all samples in a study correspond to a large amount of data. Detailed characterization requires a high sampling rate in combination with high mass resolution and wide mass range, which presents a challenge in data handling and exploration. This thesis describes methods for managing and exploring large data sets made up of such detailed 'fingerprints' (represented as data matrices). The methods were implemented as scripts and functions in Matlab, a wide-spread environment for matrix manipulations. A single-file structure to hold the imported data facilitated both easy access and fast manipulation. Routines for baseline removal and noise reduction were intended to reduce the amount of data without loosing relevant information. A tool for visualizing and exploring single runs was also included. When comparing two or more 'fingerprints' they usually have to be aligned due to unintended shifts in analyte positions in time and m/z. A PCA-like multivariate method proved to be less sensitive to such shifts, and an ANOVA implementation made it easier to find systematic differences within the data sets. The above strategies and methods were applied to complex samples such as plasma, protein digests, and urine. The field of application included urine profiling (paracetamole intake; beverage effects), peptide mapping (different digestion protocols) and search for potential biomarkers (appendicitis diagnosis) . The influence of the experimental factors was visualized by PCA score plots as well as clustering diagrams (dendrograms).
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| 10. |
- Bäckström, Daniel, 1985, et al.
(författare)
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Measurement and Modeling of Particle Radiation in Coal Flames
- 2014
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 28:3, s. 2199-2210
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Tidskriftsartikel (refereegranskat)abstract
- This work aims at developing a methodology that can provide information of in-flame particle radiation in industrial-scale flames. The method is based on a combination of experimental and modeling work. The experiments have been performed in the high-temperature zone of a 77 kWth swirling lignite flame. Spectral radiation, total radiative intensity, gas temperature, and gas composition were measured, and the radiative intensity in the furnace was modeled with an axisymmetric cylindrical radiation model using Mie theory for the particle properties and a statistical narrow-band model for the gas properties. The in-flame particle radiation was measured with a Fourier transform infrared (FTIR) spectrometer connected to a water-cooled probe via fiber optics. In the cross-section of the flame investigated, the particles were found to be the dominating source of radiation. Apart from giving information about particle radiation and temperature, the methodology can also provide estimates of the amount of soot radiation and the maximum contribution from soot radiation compared to the total particle radiation. In the center position in the flame, the maximum contribution from soot radiation was estimated to be less than 40% of the particle radiation. As a validation of the methodology, the modeled total radiative intensity was compared to the total intensity measured with a narrow angle radiometer and the agreement in the results was good, supporting the validity of the used approach.
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