| 1. |
- Bergh, Caroline, et al.
(författare)
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Organophosphate and phthalate esters in indoor air : a comparison between multi-storey buildings with high and low prevalence of sick building symptoms
- 2011
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0325 .- 1464-0333. ; 13:7, s. 2001-2009
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Tidskriftsartikel (refereegranskat)abstract
- An extensive study has been conducted of the prevalence of organophosphorous flame retardants/plasticizers and phthalate ester plasticizers in indoor air. The targeted substances were measured in 45 multi-storey apartment buildings in Stockholm, Sweden. The apartment buildings were classified as high or low risk with regard to the reporting of sick building symptoms (SBS) within the project Healthy Sustainable Houses in Stockholm (3H). Air samples were taken from two to four apartments per building (in total 169 apartments) to facilitate comparison within and between buildings. Association with building characteristics have been examined as well as association with specific sources by combining chemical analysis and exploratory uni- and multivariate data analysis. The study contributes to the overall perspective of levels of organophosphate and phthalate ester in indoor air enabling comparison with other studies. The results indicated little or no difference in the concentrations of the target substances between the two risk classifications of the buildings. The differences between the apartments sampled within (inter) buildings were greater than the differences between (intra) buildings. The concentrations measured in air ranged up to 1,200 ng/m3 for organophosphate esters and up to 11,000 ng/m3 for phthalate esters. Results in terms of sources were discerned e.g. PVC flooring is a major source of benzylbutyl phthalate in indoor air.
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| 2. |
- Olofsson, K, et al.
(författare)
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Self-perception after hypospadias repair in young men's perspective
- 2003
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Ingår i: European Journal of Plastic Surgery. - : Springer Science and Business Media LLC. - 0930-343X .- 1435-0130. ; 26:6, s. 294-297
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Tidskriftsartikel (refereegranskat)abstract
- Twenty-one males underwent an interview, clinical investigation, and measurement of urine flow and residual volume 15-25 years after surgery. Although surgical techniques have been improved during recent decades, the results of hypospadias repair made 20 years ago are nethertheless acceptable and most patients regard the outcome as satisfactory.
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| 3. |
- Otnes, Gaute, et al.
(författare)
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Understanding InP Nanowire Array Solar Cell Performance by Nanoprobe-Enabled Single Nanowire Measurements
- 2018
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:5, s. 3038-3046
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Tidskriftsartikel (refereegranskat)abstract
- III-V solar cells in the nanowire geometry might hold significant synthesis-cost and device-design advantages as compared to thin films and have shown impressive performance improvements in recent years. To continue this development there is a need for characterization techniques giving quick and reliable feedback for growth development. Further, characterization techniques which can improve understanding of the link between nanowire growth conditions, subsequent processing, and solar cell performance are desired. Here, we present the use of a nanoprobe system inside a scanning electron microscope to efficiently contact single nanowires and characterize them in terms of key parameters for solar cell performance. Specifically, we study single as-grown InP nanowires and use electron beam induced current characterization to understand the charge carrier collection properties, and dark current-voltage characteristics to understand the diode recombination characteristics. By correlating the single nanowire measurements to performance of fully processed nanowire array solar cells, we identify how the performance limiting parameters are related to growth and/or processing conditions. We use this understanding to achieve a more than 7-fold improvement in efficiency of our InP nanowire solar cells, grown from a different seed particle pattern than previously reported from our group. The best cell shows a certified efficiency of 15.0%; the highest reported value for a bottom-up synthesized InP nanowire solar cell. We believe the presented approach have significant potential to speed-up the development of nanowire solar cells, as well as other nanowire-based electronic/optoelectronic devices.
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| 4. |
- Savolainen, Johannes, et al.
(författare)
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Structured intervention plan including component-resolved diagnostics helps reducing the burden of food allergy among school-aged children
- 2019
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Ingår i: Pediatric Allergy and Immunology. - : WILEY. - 0905-6157 .- 1399-3038. ; 30:1, s. 99-106
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Tidskriftsartikel (refereegranskat)abstract
- Background Food allergies can substantially burden patients and families by negatively affecting finances, social relationships, and personal perceptions of health. This study was performed under the Finnish Allergy Programme aimed at reducing avoidance diets to foods in schoolchildren by 50%. The main goal of this study was to investigate how many children could be freed from diet restrictions in a Finnish school district through a diagnostic algorithm including component-resolved diagnostics and food challenge. The secondary aim was to provide a crude estimate of the burden of the elimination food diets in the region, and the savings associated with the proposed intervention. Methods A total of 205 children on a food avoidance diet according to the school register because of food allergy were invited into the study. One hundred and fifty-seven children were interviewed, tested for IgE to extracts and allergen components and food challenged in respective order. Results After two years, 12 children still had an avoidance diet and three of them were treated successfully with sOTI; the rest suspended their avoidance diet (n = 134) or dropped out of the study (n = 11). The cost of the elimination diets was estimated in 172 700euro per year at start and 13 200euro per year at the end of the study; total savings were 128 400euro yearly. Conclusions The results demonstrate a 65% reduction of avoidance diets to foods in school-aged children, exceeding the 50% aim of the Finnish Allergy Programme. Therefore, it is possible to actively reduce the number of food allergy diagnoses that remain unmonitored in the society through a tailored diagnostic work-up.
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| 5. |
- Yamamoto-Hanada, Kiwako, et al.
(författare)
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IgE responses to multiple allergen components among school-aged children in a general population birth cohort in Tokyo
- 2020
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Ingår i: World Allergy Organization Journal. - : Elsevier. - 1939-4551. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Background: Response patterns to allergen components among Japanese children have not been studied extensively. Objective: Our aim was to examine the differences in sensitization patterns at ages 5 years and 9 years to identify longitudinal changes in the degree and patterns of sensitization in a birth cohort of Japanese children. Methods: Our study enrolled 984 children at aged 5 years between 2008 and 2010, and 729 children aged 9 years between 2012 and 2014. Allergic diseases were assessed using the ISAAC and UK Working Party's Diagnostic Criteria. Serum-specific IgE titers to allergen components were measured by multiplex array ImmunoCAP ISAC when the children were aged 5 and 9 years. Principal component analysis (PCA) was performed to characterize IgE sensitization to allergen components. Results: The prevalence of allergic rhinitis increased considerably over time (10.6%-31.2%). Furthermore, the sensitization prevalence to allergen-specific IgE (sIgE) also increased from 57.8% at age 5 years to 74.8% at age 9 years. IgE sensitization prevalence to Der f 1 (mites) was 42.1% at age 5 years and 54.3% at age 9 years. Furthermore, children were highly sensitized to Cry j 1 (Japanese cedar) (32.8% at age 5 years and 57.8% at age 9 years). Principle component analysis showed that sensitization to PR-10 cross-reactive components was independent of sensitization to mite and that no children acquired sensitization to pollen before acquiring sensitization to mite. Conclusions: The prevalence of allergic rhinitis and related allergen components increased from age 5 years to age 9 years in Japanese children.
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| 6. |
- Åberg, Anna, et al.
(författare)
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Helicobacter pylori adapts to chronic infection and gastric disease via ph-responsive baba-mediated adherence
- 2017
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Ingår i: Cell Host and Microbe. - : Elsevier BV. - 1931-3128 .- 1934-6069. ; 21:3, s. 376-389
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Tidskriftsartikel (refereegranskat)abstract
- The BabA adhesin mediates high-affinity binding of Helicobacter pylori to the ABO blood group antigen-glycosylated gastric mucosa. Here we show that BabA is acid responsive-binding is reduced at low pH and restored by acid neutralization. Acid responsiveness differs among strains; often correlates with different intragastric regions and evolves during chronic infection and disease progression; and depends on pH sensor sequences in BabA and on pH reversible formation of high-affinity binding BabA multimers. We propose that BabA's extraordinary reversible acid responsiveness enables tight mucosal bacterial adherence while also allowing an effective escape from epithelial cells and mucus that are shed into the acidic bactericidal lumen and that bio-selection and changes in BabA binding properties through mutation and recombination with babA-related genes are selected by differences among individuals and by changes in gastric acidity over time. These processes generate diverse H. pylori subpopulations, in which BabA's adaptive evolution contributes to H. pylori persistence and overt gastric disease.
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| 7. |
- Alm, Erik, 1980-, et al.
(författare)
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A solution to the 1D NMR alignment problem using an extended generalized fuzzy Hough transform and mode support
- 2009
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 395:1, s. 213-223
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Tidskriftsartikel (refereegranskat)abstract
- This paper approaches the problem of intersample peak correspondence in the context of later applying statistical data analysis techniques to 1D 1H-nuclear magnetic resonance (NMR) data. Any data analysis methodology will fail to produce meaningful results if the analyzed data table is not synchronized, i.e., each analyzed variable frequency (Hz) does not originate from the same chemical source throughout the entire dataset. This is typically the case when dealing with NMR data from biological samples. In this paper, we present a new state of the art for solving this problem using the generalized fuzzy Hough transform (GFHT). This paper describes significant improvements since the method was introduced for NMR datasets of plasma in Csenki et al. (Anal Bioanal Chem 389:875-885, 15) and is now capable of synchronizing peaks from more complex datasets such as urine as well as plasma data. We present a novel way of globally modeling peak shifts using principal component analysis, a new algorithm for calculating the transform and an effective peak detection algorithm. The algorithm is applied to two real metabonomic 1H-NMR datasets and the properties of the method are compared to bucketing. We implicitly prove that GFHT establishes the objectively true correspondence. Desirable features of the GFHT are: (1) intersample peak correspondence even if peaks change order on the frequency axis and (2) the method is symmetric with respect to the samples.
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| 8. |
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| 9. |
- Alm, Erik, 1980-, et al.
(författare)
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Automated annotation and quantification of metabolites in (1)H NMR data of biological origin
- 2012
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 403:2, s. 443-455
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Tidskriftsartikel (refereegranskat)abstract
- In 1H NMR metabolomic datasets, there are often over a thousand peaks per spectrum, many of which change position drastically between samples. Automatic alignment, annotation, and quantification of all the metabolites of interest in such datasets have not been feasible. In this work we propose a fully automated annotation and quantification procedure which requires annotation of metabolites only in a single spectrum. The reference database built from that single spectrum can be used for any number of 1H NMR datasets with a similar matrix. The procedure is based on the generalized fuzzy Hough transform (GFHT) for alignment and on Principal-components analysis (PCA) for peak selection and quantification. We show that we can establish quantities of 21 metabolites in several 1H NMR datasets and that the procedure is extendable to include any number of metabolites that can be identified in a single spectrum. The procedure speeds up the quantification of previously known metabolites and also returns a table containing the intensities and locations of all the peaks that were found and aligned but not assigned to a known metabolite. This enables both biopattern analysis of known metabolites and data mining for new potential biomarkers among the unknowns.
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| 10. |
- Alm, Erik, 1980-, et al.
(författare)
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Time-resolved biomarker discovery inH-NMR data using generalized fuzzy Hough transform alignment and parallel factor analysis
- 2010
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 396:5, s. 1681-1689
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Tidskriftsartikel (refereegranskat)abstract
- This work addresses the subject of time-series analysis of comprehensive 1H-NMR data of biological origin. One of the problems with toxicological and efficacy studies is the confounding of correlation between the administered drug, its metabolites and the systemic changes in molecular dynamics, i.e., the flux of drug-related molecules correlates with the molecules of system regulation. This correlation poses a problem for biomarker mining since this confounding must be untangled in order to separate true biomarker molecules from dose-related molecules. One way of achieving this goal is to perform pharmacokinetic analysis. The difference in pharmacokinetic time profiles of different molecules can aid in the elucidation of the origin of the dynamics, this can even be achieved regardless of whether the identity of the molecule is known or not. This mode of analysis is the basis for metabonomic studies of toxicology and efficacy. One major problem concerning the analysis of 1H-NMR data generated from metabonomic studies is that of the peak positional variation and of peak overlap. These phenomena induce variance in the data, obscuring the true information content and are hence unwanted but hard to avoid. Here, we show that by using the generalized fuzzy Hough transform spectral alignment, variable selection, and parallel factor analysis, we can solve both the alignment and the confounding problem stated above. Using the outlined method, several different temporal concentration profiles can be resolved and the majority of the studied molecules and their respective fluxes can be attributed to these resolved kinetic profiles. The resolved time profiles hereby simplifies finding true biomarkers and bio-patterns for early detection of biological conditions as well as providing more detailed information about the studied biological system. The presented method represents a significant step forward in time-series analysis of biological 1H-NMR data as it provides almost full automation of the whole data analysis process and is able to analyze over 800 unique features per sample. The method is demonstrated using a 1H-NMR rat urine dataset from a toxicology study and is compared with a classical approach: COW alignment followed by bucketing.
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| 11. |
- Csenki, Leonard, et al.
(författare)
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Proof of principle of a generalized fuzzy Hough transform approach to peak alignment of one-dimensional 1H NMR data
- 2007
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 389:3, s. 875-885
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Tidskriftsartikel (refereegranskat)abstract
- In metabolic profiling, multivariate data analysis techniques are used to interpret one-dimensional (1D) 1H NMR data. Multivariate data analysis techniques require that peaks are characterised by the same variables in every spectrum. This location constraint is essential for correct comparison of the intensities of several NMR spectra. However, variations in physicochemical factors can cause the locations of the peaks to shift. The location prerequisite may thus not be met, and so, to solve this problem, alignment methods have been developed. However, current state-of-the-art algorithms for data alignment cannot resolve the inherent problems encountered when analysing NMR data of biological origin, because they are unable to align peaks when the spatial order of the peaks changes—a commonly occurring phenomenon. In this paper a new algorithm is proposed, based on the Hough transform operating on an image representation of the NMR dataset that is capable of correctly aligning peaks when existing methods fail. The proposed algorithm was compared with current state-of-the-art algorithms operating on a selected plasma dataset to demonstrate its potential. A urine dataset was also processed using the algorithm as a further demonstration. The method is capable of successfully aligning the plasma data but further development is needed to address more challenging applications, for example urine data.
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| 12. |
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| 13. |
- Grigoriadis, Anastasios, et al.
(författare)
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Effect of Sudden Deprivation of Sensory Inputs From Periodontium on Mastication
- 2019
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Ingår i: Frontiers in Neuroscience. - : Frontiers Media SA. - 1662-4548 .- 1662-453X. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To investigate the effect of sudden deprivation of sensory inputs from the periodontium on jaw kinematics and time-varying activation profile of the masseter muscle.Methods: Fourteen (age range: 22-26 years; four men) healthy and natural dentate volunteers participated in a single experimental session. During the experiment, the participants were asked to eat six hard visco-elastic test food models, three each before and after an anesthetic intervention. The movements of the jaw in three dimensions and electromyographic (EMG) activity of the masseter muscle on the chewing side were recorded.Results: The results of the study showed no significant differences in the number of chewing cycles (P = 0.233) and the duration of chewing sequence (P = 0.198) due to sudden deprivation of sensory inputs from the periodontium. However, there was a significant increase in the jaw opening velocity (P = 0.030) and a significant increase in the duration of occlusal phase (P = 0.004) during the anesthetized condition. The EMG activity of the jaw closing phase was significantly higher during the control condition [116.5 arbitrary units (AU)] than anesthetized condition (93.9 AU). The temporal profile of the masseter muscle showed a biphasic increase in the excitatory muscle drive in the control condition but this increase was virtually absent during the anesthetized condition.Conclusion: Sudden deprivation of sensory inputs from the periodontium affects the jaw kinematics and jaw muscle activity, with a clear difference in the time-varying activation profile of the masseter muscle. The activation profile of the masseter muscle shows that periodontal mechanoreceptors contribute to approximately 20% of the EMG activity during the jaw closing phase.
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| 14. |
- Jiang, Liying, et al.
(författare)
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Strategy for quantifying trace levels of BMAA in cyanobacteria by LC/MS/MS
- 2013
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 405:4, s. 1283-1292
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Tidskriftsartikel (refereegranskat)abstract
- The cyanobacterial neurotoxin β-N-methylamino--alanine (BMAA) is an amino acid that is putatively associated with the pathology of amyotrophic lateral sclerosis/Parkinsonism –dementia complex (ALS-PDC) disease. It raises serious health risk concerns since cyanobacteria are ubiquitous thus making human exposure almost inevitable. The identification and quantification of BMAA in cyanobacteria is challenging because it is present only in trace amounts and occurs alongside structurally similar compounds such as BMAA isomers. This work describes an enhanced liquid chromatography/tandem mass spectrometry platform that can distinguish BMAA from its isomers β-amino-N-methyl-alanine, N-(2-oethyl) glycine (AEG), and 2,4-diaminobutyric acid, thus ensuring confident identification of BMAA. The method's sensitivity was improved fourfold by a post-column addition of acetonitrile. The instrument and method limits of detection were shown to be 4.2 fmol/injection (or 0.5 g/one column) and 0.1 μg/g dry weight of cyanobacteria, respectively. The quantification method uses synthesized deuterated BMAA as an internal standard and exhibits good linearity, accuracy, and precision. Matrix effects were also investigated, revealing an ion enhancement of around 18 %. A lab-cultured cyanobacterial sample (Leptolyngbya PCC73110) was analyzed and shown to contain about 0.73 μg/g dry weight BMAA. The isomer AEG, whose chromatographic properties closely resemble those of BMAA, was also detected. These results highlight the importance of distinguishing BMAA from its isomers for reliable identification as well as providing a sensitive and accurate quantification method for measuring trace levels of BMAA in cyanobacterial samples.
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| 15. |
- Midhagen, Gunnar, et al.
(författare)
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Antibody levels in adult patients with coeliac disease during gluten free diet a rapid initial decrease of clinical importance
- 2004
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 256:6, s. 519-524
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Analysis of antibodies against tissue transglutaminase (tTG) has been shown valuable in the diagnosis of coeliac disease (CD) but how quickly serum titres decrease after introduction of a gluten-free diet (GFD) is not known in adults. CD is a well-recognized disorder amongst the general population and many persons try a GFD for fairly vague symptoms before they seek medical advice. Therefore, it is important to determine the time that the serologic tests remain predictive of the disease after the introduction of a GFD. Methods. Sera were taken from 22 consecutively biopsy-proven adult patients with CD in connection with the diagnostic biopsy. The patients were followed for 1 year and sera were taken after 1, 3, 6 and 12 months after start of a GFD. Sera were stored at −20 °C and analysed for IgA antibodies against gliadin, endomysium and two different commercial tTG assays based on recombinant human tTG (tTGrh) and guinea-pig liver (tTGgp). Results. Twenty patients could be followed during GFD and all antibody titres fell sharply within 1 month after introduction of a GFD and continued to decline during the survey interval. Thirty days after beginning the diet only 58, 84, 74 and 53% of all patients had positive antibody levels of tTGrh, tTGgp, EmA and AGA respectively. Conclusions. As the antibodies used to confirm the diagnosis of CD fall rapidly and continue to decline following the introduction of a GFD, it is important that health care providers carefully inquire about the possibility of self-prescribed diets before patients sought medical attention.
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| 16. |
- Mie, Axel, et al.
(författare)
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Discrimination of conventional and organic white cabbage from a long-term field trial study using untargeted LC-MS-based metabolomics
- 2014
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 406:12, s. 2885-2897
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Tidskriftsartikel (refereegranskat)abstract
- The influence of organic and conventional farming practices on the content of single nutrients in plants is disputed in the scientific literature. Here, large-scale untargeted LC-MS-based metabolomics was used to compare the composition of white cabbage from organic and conventional agriculture, measuring 1,600 compounds. Cabbage was sampled in 2 years from one conventional and two organic farming systems in a rigidly controlled long-term field trial in Denmark. Using Orthogonal Projection to Latent Structures–Discriminant Analysis (OPLS-DA), we found that the production system leaves a significant (p = 0.013) imprint in the white cabbage metabolome that is retained between production years. We externally validated this finding by predicting the production system of samples from one year using a classification model built on samples from the other year, with a correct classification in 83 % of cases. Thus, it was concluded that the investigated conventional and organic management practices have a systematic impact on the metabolome of white cabbage. This emphasizes the potential of untargeted metabolomics for authenticity testing of organic plant products.
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| 17. |
- Mzezewa, S, et al.
(författare)
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A prospective double blind randomized study comparing the need for blood transfusion with terlipressin or a placebo during early excision and grafting of burns
- 2004
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Ingår i: Burns. - : Elsevier BV. - 0305-4179. ; 30:3, s. 236-240
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Early excision and skin grafting has become the standard of good burn management, but it is associated with major blood loss. Aim: To determine the haemostatic effect of terlipressin compared with placebo. Material and methods: Fifty-one patients with bums of 10-20% total body surface area had early excision and split skin grafting of deep burns. The surface area of the bum wound and of the heated graft were measured by planimetry. The patients were randomly allocated to medication, either terlipressin or placebo. Blood loss and number of transfused units of blood were recorded. Results: Twenty-one patients received terlipressin, 13 received terlipressin late (cross-over) and 17 received placebo. Six out of 21 patients exposed to terlipressin were transfused with eleven units of packed red blood cells. Seven out of 13 patients crossed over from placebo to terlipressin (late terlipressin) were transfused with 17 units of blood. Eight out of 17 patients exposed to the placebo were transfused with 22 units of blood (P < 0.05). Graft healing was 1055 +/- 609 cm(2) out of 1452 +/- 1811 cm(2) in terlipressin and 914 +/- 633 cm(2) out of 1288 720 cm 2 in the placebo group (n.s.). Conclusion: Terlipressin reduced the need for blood transfusion by a factor of 2.5 compared to a placebo without impairment of graft healing.
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| 18. |
- Mzezewa, S, et al.
(författare)
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HIV infection reduces skin graft survival in burn injuries: a prospective study
- 2003
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Ingår i: British Journal of Plastic Surgery. - : Elsevier BV. - 1465-3087 .- 0007-1226. ; 56:8, s. 740-745
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Tidskriftsartikel (refereegranskat)abstract
- Impaired survival of skin grafts has been noted in human immunodeficiency virus (HIV) infected patients, but the reason is not known. Alterations in inflammatory response, which might be recorded as an imbalance in cytokine production, have been implicated. The aim of this study was to determine the impact of HIV infection in patients with burn injuries by comparison of split skin graft survival, T lymphocyte count and cytokine levels in HIV-infected and non HIV-infected patients in relation to healthy and HIV-infected nonburnt volunteers. Fifty-four patients with deep dermal burns were included. Fifteen patients' were HIV-infected. Thirteen healthy and 15 HIV-infected, volunteers were recruited as controls. The burnt surface area was traced on a transparent plastic sheet and converted to area. Graft survival on day of discharge/regraft for non HIV-infected patients was 69%, and in HIV-infected 22%, (p < 0.05). The median length of hospital stay for early excision among non HIV-infected patients was 21 (12-53) days and for HIV-infected, 41 days (p < 0.05). Serum protein levels in HIV-infected patients were elevated compared to non HIV-infected patients (p < 0.05). CD4+ Lymphocytes were depressed in HIV-infected volunteers and HIV-infected burn patients compared to healthy volunteers (p < 0.05). CD8+ lymphocytes were elevated in HIV-infected volunteers compared to non HIV-infected burn patients. Pro-inflammatory cytokine levels of Interleukin-2 (IL-2), Interteukin-6 (IL-6), Interferon-gama (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha) were depressed in HIV-infected volunteers compared to healthy volunteers and non HIV-infected burn patients. The pro-inflammatory cytokine IFN-gamma did not increase after burn injury in HIV-infected burns patients as did IL-2, IL-6 and TNF-alpha (p < 0.05). Antiinflammatory cytokine levels of IL-4 were elevated in HIV-infected volunteers compared to healthy volunteers and burn patients (p < 0.05). Conclusion: Graft survival after split skin grafting of burn wounds in HIV-infected patients is impaired and hospital stay is prolonged. HIV infection. result in immune dysregulation, which might be related to impaired skin graft survival. (C) 2003 The British Association of Plastic Surgeons. Published by Elsevier Ltd. ALL rights reserved.
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| 19. |
- Plassmann, Merle M., et al.
(författare)
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Non-target time trend screening : a data reduction strategy for detecting emerging contaminants in biological samples
- 2016
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 408:16, s. 4203-4208
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Tidskriftsartikel (refereegranskat)abstract
- Non-targeted mass spectrometry-based approaches for detecting novel xenobiotics in biological samples are hampered by the occurrence of naturally fluctuating endogenous substances, which are difficult to distinguish from environmental contaminants. Here, we investigate a data reduction strategy for datasets derived from a biological time series. The objective is to flag reoccurring peaks in the time series based on increasing peak intensities, thereby reducing peak lists to only those which may be associated with emerging bioaccumulative contaminants. As a result, compounds with increasing concentrations are flagged while compounds displaying random, decreasing, or steady-state time trends are removed. As an initial proof of concept, we created artificial time trends by fortifying human whole blood samples with isotopically labelled standards. Different scenarios were investigated: eight model compounds had a continuously increasing trend in the last two to nine time points, and four model compounds had a trend that reached steady state after an initial increase. Each time series was investigated at three fortification levels and one unfortified series. Following extraction, analysis by ultra performance liquid chromatography high-resolution mass spectrometry, and data processing, a total of 21,700 aligned peaks were obtained. Peaks displaying an increasing trend were filtered from randomly fluctuating peaks using time trend ratios and Spearman's rank correlation coefficients. The first approach was successful in flagging model compounds spiked at only two to three time points, while the latter approach resulted in all model compounds ranking in the top 11 % of the peak lists. Compared to initial peak lists, a combination of both approaches reduced the size of datasets by 80-85 %. Overall, non-target time trend screening represents a promising data reduction strategy for identifying emerging bioaccumulative contaminants in biological samples.
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| 20. |
- Sousa, Pedro F. M., et al.
(författare)
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Can we beat overfitting?-A closer look at Cloarec's PLS algorithm
- 2018
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Ingår i: Journal of Chemometrics. - : Wiley. - 0886-9383 .- 1099-128X. ; 32:6
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Tidskriftsartikel (refereegranskat)abstract
- Random noise has been addressed as a cause of overfitting in partial least squares regression. A previous study pinpointed that one of the sources of overfitting resides in the calculation of scores due to the accumulation of noise in the diagonal of the variance-covariance matrix, and a modified partial least squares regression was proposed with the removal of this diagonal prior to the score calculation. Here, a further modification of the NIPALS algorithm is proposed, with the same ability to overcome overfitting due to noise, but algebraically more similar to the original NIPALS. The results indicate that it is possible to get more reliable auto-prediction R-2 with a cross-validation performance close to that of the original NIPALS algorithm.
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| 21. |
- Sousa, Pedro F. M., et al.
(författare)
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Elucidation of chromatographic peak shifts in complex samples using a chemometrical approach
- 2018
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 410:21, s. 5229-5235
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Tidskriftsartikel (refereegranskat)abstract
- Chromatographic retention time peak shifts between consecutive analyses is a well-known fact yet not fully understood. Algorithms have been developed to align peaks between runs, but with no specific studies considering the causes of peak shifts. Here, designed experiments reveal chromatographic shift patterns for a complex peptide mixture that are attributable to the temperature and pH of the mobile phase. These results demonstrate that peak shifts are highly structured and are to a high degree explained by underlying differences in physico-chemical parameters of the chromatographic system and also provide experimental support for the alignment algorithm called the generalized fuzzy Hough transform which exploits this fact. It can be expected that the development of alignment algorithms enters a new phase resulting in increasingly accurate alignment by considering the latent structure of the peak shifts.
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| 22. |
- Tengstrand, Erik, et al.
(författare)
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A concept study on non-targeted screening for chemical contaminants in food using liquid chromatography–mass spectrometry in combination with a metabolomics approach
- 2013
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 405:4, s. 1237-1243
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Tidskriftsartikel (refereegranskat)abstract
- A generic method to screen for new or unexpected contaminants at ppm levels in food has been developed. The method comprises an acidic acetonitrile extraction, detection with ultra-high-pressure liquid chromatography coupled to electrospray ionisation time-of-flight mass spectrometry and statistical evaluation using a metabolomics approach comparing suspected contaminated food with uncontaminated foods. The method was tested for 26 model contaminants from 100 μg/g down to 0.4 μg/g in three brands of fresh orange juice. Blinded statistical evaluation revealed signals from all added contaminants detectable by liquid chromatography –electrospray ionisation using positive ionisation mode, while only two false-positive signals were reported. The method is primarily intended to be used for investigation of food samples suspected to be contaminated with unknown substances. Additionally it could be used to continuously monitor for appearance of new food contaminants as a complement to the specific targeted analysis that is today’s foundation of food safety analysis.
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| 23. |
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| 24. |
- Tengstrand, Erik, et al.
(författare)
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TracMass 2-A Modular Suite of Tools for Processing Chromatography-Full Scan Mass Spectrometry Data
- 2014
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 86:7, s. 3435-3442
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Tidskriftsartikel (refereegranskat)abstract
- In untargeted proteomics and metabolomics, raw data obtained with an LC/MS instrument are processed into a format that can be used for statistical analysis. Full scan MS data from chromatographic separation of biological samples are complex and analyte concentrations need to be extracted and aligned so that they can be compared across the samples. Several computer programs and methods have been developed for this purpose. There is still a need to improve the ease of use and feedback to the user because of the advanced multi-parametric algorithms used. Here, we present and make publicly available, TracMass 2, a suite of computer programs that gives immediate graphical feedback to the data analyst on parameter settings and processing results, as well as producing state-of-the-art results. The main advantage of TracMass 2 is that the feedback and transparency of the processing steps generate confidence in the end result, which is a table of peak intensities. The data analyst can easily validate every step of the processing pipeline. Because the user receives feedback on how all parameter values affect the result before starting a lengthy computation, the user's learning curve is enhanced and the total time used for data processing can be reduced. TracMass 2 has been released as open source and is included in the Supporting Information. We anticipate that TracMass 2 will set a new standard for how chemometrical algorithms are implemented in computer programs.
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| 25. |
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| 26. |
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| 27. |
- Åberg, K. Magnus, et al.
(författare)
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Extensions to peak alignment using reduced set mapping and classification of LC-UV data from peptide mapping
- 2005
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Ingår i: Journal of Chemometrics. - : Wiley InterScience. - 0886-9383 .- 1099-128X. ; 18:10, s. 465-473
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Tidskriftsartikel (refereegranskat)abstract
- Peak alignment using reduced set mapping (PARS) is extended with a new baseline approximation and a new dendrogram alignment scheme, which is designed to avoid the issue of selecting a target chromatogram for the alignment. Two data sets with LC/UV data are studied and it is shown that peak alignment with PARS increases the class separation substantially in the principal component score space. The results indicate that it is possible to use PARS for calibration transfer of multivariate models of chromatographic data.
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| 28. |
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| 29. |
- Åberg, K. Magnus, 1976-
(författare)
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Variance Reduction in Analytical Chemistry : New Numerical Methods in Chemometrics and Molecular Simulation
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is based on five papers addressing variance reduction in different ways. The papers have in common that they all present new numerical methods.Paper I investigates quantitative structure-retention relationships from an image processing perspective, using an artificial neural network to preprocess three-dimensional structural descriptions of the studied steroid molecules.Paper II presents a new method for computing free energies. Free energy is the quantity that determines chemical equilibria and partition coefficients. The proposed method may be used for estimating, e.g., chromatographic retention without performing experiments.Two papers (III and IV) deal with correcting deviations from bilinearity by so-called peak alignment. Bilinearity is a theoretical assumption about the distribution of instrumental data that is often violated by measured data. Deviations from bilinearity lead to increased variance, both in the data and in inferences from the data, unless invariance to the deviations is built into the model, e.g., by the use of the method proposed in paper III and extended in paper IV.Paper V addresses a generic problem in classification; namely, how to measure the goodness of different data representations, so that the best classifier may be constructed. Variance reduction is one of the pillars on which analytical chemistry rests. This thesis considers two aspects on variance reduction: before and after experiments are performed. Before experimenting, theoretical predictions of experimental outcomes may be used to direct which experiments to perform, and how to perform them (papers I and II). After experiments are performed, the variance of inferences from the measured data are affected by the method of data analysis (papers III-V).
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