| 1. |
- Brännvall, Elisabet, et al.
(författare)
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The balance between alkali diffusion and alkali consuming reactions during impregnation of softwood. Impregnation for kraft pulping revisited
- 2018
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 72:3, s. 169-178
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the impregnation stage is to ensure that cooking chemicals reach all parts of the chips. However, as alkali comes into contact with wood, reactions take place, which alter the paths available for ionic transport and dissolve wood components. The aim of the present study is to establish the most favorable impregnation conditions, which result in an even alkali concentration profile through the chip at a sufficiently high level without extensive yield losses due to peeling. Softwood chips were subjected to different impregnation conditions. The progress of impregnation was assessed by analyzing the concentration of hydroxide ions in the bound liquor inside wood chips and the release of acetic acid. The extent of undesired reactions was measured as the amount of carbohydrate degradation products formed and amount of wood dissolved. Increased temperature and time lead to more degradation of the carbohydrates during impregnation. At high temperature, the concentration of alkali in the bound liquor was lower due to higher alkali consumption in degradation reactions. The most favorable process is to perform impregnation at an elevated initial effective alkali (EA) for a short time. This resulted in an increased alkali concentration in the bound liquor within the chip without extensive carbohydrate degradation.
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| 2. |
- De Marinis, Yang, et al.
(författare)
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GLP-1 inhibits and adrenaline stimulates glucagon release by differential modulation of N- and L-type Ca2+ channel-dependent exocytosis.
- 2010
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 11:6, s. 543-553
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Tidskriftsartikel (refereegranskat)abstract
- Glucagon secretion is inhibited by glucagon-like peptide-1 (GLP-1) and stimulated by adrenaline. These opposing effects on glucagon secretion are mimicked by low (1-10 nM) and high (10 muM) concentrations of forskolin, respectively. The expression of GLP-1 receptors in alpha cells is <0.2% of that in beta cells. The GLP-1-induced suppression of glucagon secretion is PKA dependent, is glucose independent, and does not involve paracrine effects mediated by insulin or somatostatin. GLP-1 is without much effect on alpha cell electrical activity but selectively inhibits N-type Ca(2+) channels and exocytosis. Adrenaline stimulates alpha cell electrical activity, increases [Ca(2+)](i), enhances L-type Ca(2+) channel activity, and accelerates exocytosis. The stimulatory effect is partially PKA independent and reduced in Epac2-deficient islets. We propose that GLP-1 inhibits glucagon secretion by PKA-dependent inhibition of the N-type Ca(2+) channels via a small increase in intracellular cAMP ([cAMP](i)). Adrenaline stimulates L-type Ca(2+) channel-dependent exocytosis by activation of the low-affinity cAMP sensor Epac2 via a large increase in [cAMP](i).
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| 3. |
- Gonzalez de Vega, Raquel, et al.
(författare)
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A multi-platform approach for the comprehensive analysis of per- and polyfluoroalkyl substances (PFAS) and fluorine mass balance in commercial ski wax products
- 2024
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Ingår i: Analytica Chimica Acta. - : Elsevier B.V.. - 0003-2670 .- 1873-4324. ; 1314
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Tidskriftsartikel (refereegranskat)abstract
- The unique properties of per- and polyfluoroalkyl substances (PFAS) have led to their extensive use in consumer products, including ski wax. Based on the risks associated with PFAS, and to align with PFAS regulations, the international ski federation (FIS) implemented a ban on products containing “C8 fluorocarbons/perfluorooctanoate (PFOA)” at all FIS events from the 2021/2022 season, leading manufactures to shift their formulations towards short-chain PFAS chemistries. To date, most studies characterising PFAS in ski waxes have measured a suite of individual substances using targeted analytical approaches. However, the fraction of total fluorine (TF) in the wax accounted for by these substances remains unclear. In this study, we sought to address this question by applying a multi-platform, fluorine mass balance approach to a total of 10 commercially available ski wax products. Analysis of TF by combustion ion chromatography (CIC) revealed concentrations of 1040–51700 μg F g−1 for the different fluorinated waxes. In comparison, extractable organic fluorine (EOF) determined in methanol extracts by CIC (and later confirmed by inductively-coupled plasma-mass spectrometry and 19F- nuclear magnetic resonance spectroscopy) ranged from 92 to 3160 μg g−1, accounting for only 3–8.8 % of total fluorine (TF). Further characterisation of extracts by cyclic ion mobility-mass spectrometry (IMS) revealed 15 individual PFAS with perfluoroalkyl carboxylic acid concentrations up to 33 μg F g−1, and 3 products exceeding the regulatory limit for PFOA (0.025 μg g−1) by a factor of up to 100. The sum of all PFAS accounted for only 0.01–1.0 % of EOF, implying a high percentage of unidentified PFAS, thus, pyrolysis gas chromatography-mass spectrometry was used to provide evidence of the nature of the non-extractable fluorine present in the ski wax products.
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| 4. |
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| 5. |
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| 6. |
- Li, Jia, et al.
(författare)
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Submembrane ATP and Ca2+ kinetics in alpha-cells : unexpected signaling for glucagon secretion
- 2015
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Ingår i: The FASEB Journal. - : Wiley. - 0892-6638 .- 1530-6860. ; 29:8, s. 3379-3388
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Tidskriftsartikel (refereegranskat)abstract
- Cytoplasmic ATP and Ca2+ are implicated in current models of glucose's control of glucagon and insulin secretion from pancreatic alpha- and beta-cells, respectively, but little is known about ATP and its relation to Ca2+ in alpha-cells. We therefore expressed the fluorescent ATP biosensor Perceval in mouse pancreatic islets and loaded them with a Ca2+ indicator. With total internal reflection fluorescence microscopy, we recorded subplasma membrane concentrations of Ca2+ and ATP ([Ca2+](pm); [ATP](pm)) in superficial alpha- and beta-cells of intact islets and related signaling to glucagon and insulin secretion by immunoassay. Consistent with ATP's controlling glucagon and insulin secretion during hypo- and hyperglycemia, respectively, the dose-response relationship for glucoseinduced [ATP](pm) generation was left shifted in alpha-cells compared to beta-cells. Both cell types showed [Ca2+](pm) and [ATP](pm) oscillations in opposite phase, probably reflecting energy-consuming Ca2+ transport. Although pulsatile insulin and glucagon release are in opposite phase, [Ca2+](pm) synchronized in the same phase between alpha- and beta-cells. This paradox can be explained by the overriding of Ca2+ stimulation by paracrine inhibition, because somatostatin receptor blockade potently stimulated glucagon release with little effect on Ca2+. The data indicate that an alpha-cell-intrinsic mechanism controls glucagon in hypoglycemia and that paracrine factors shape pulsatile secretion in hyperglycemia.
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| 7. |
- Nethander, Maria, 1980, et al.
(författare)
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An atlas of genetic determinants of forearm fracture.
- 2023
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Ingår i: Nature genetics. - : Springer Nature. - 1546-1718 .- 1061-4036. ; 55:11, s. 1820-1830
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Tidskriftsartikel (refereegranskat)abstract
- Osteoporotic fracture is among the most common and costly of diseases. While reasonably heritable, its genetic determinants have remained elusive. Forearm fractures are the most common clinically recognized osteoporotic fractures with a relatively high heritability. To establish an atlas of the genetic determinants of forearm fractures, we performed genome-wide association analyses including 100,026 forearm fracture cases. We identified 43 loci, including 26 new fracture loci. Although most fracture loci associated with bone mineral density, we also identified loci that primarily regulate bone quality parameters. Functional studies of one such locus, at TAC4, revealed that Tac4-/- mice have reduced mechanical bone strength. The strongest forearm fracture signal, at WNT16, displayed remarkable bone-site-specificity with no association with hip fractures. Tall stature and low body mass index were identified as new causal risk factors for fractures. The insights from this atlas may improve fracture prediction and enable therapeutic development to prevent fractures.
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| 8. |
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| 9. |
- Olsson, Carina, et al.
(författare)
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Carbon fibres from lignin-cellulose precursor
- 2015
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Ingår i: 18th International Symposium on Wood, Fiber and Pulping Chemistry, September 9-11, 2015, Vienna. ; , s. 126-129
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A series of two-component precursor fibres for carbon fibre production has been produced by air-gap spinning of kraft lignin with cellulose as the fibreforming polymer, the latter from paper grade or dissolving grade pulps. The spun precursor fibres,containing 70% lignin and 30% cellulose, demonstrate mechanical properties equivalent to commercial textile fibres. Precursor fibres based on softwood kraft lignin were treated thermally in twosteps to carbon fibres, which had mechanical properties equal to or greater than those reported for neat lignin-based carbon fibres produced by melt spinning. An advantage of the wet-spun precursor fibres developed in this project is that they are more flexible and easier to handle with a decreased risk ofbrittle fracture. The potential for further improvement for the new type of carbon fibre is very high.
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| 10. |
- Olsson, Carina, et al.
(författare)
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Carbon fibres from precursors produced by dry-jet wet-spinning of kraft lignin blended with kraft pulps
- 2017
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Ingår i: Holzforschung. - : Walter de Gruyter GmbH. - 0018-3830 .- 1437-434X. ; 71:4, s. 275-283
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Tidskriftsartikel (refereegranskat)abstract
- A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFS) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFS made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFS based on dry-jet wet-spun precursors still have a high potential for further improvements.
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| 11. |
- Rönnols, Jerk, et al.
(författare)
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Structural changes in softwood kraft lignin during nonoxidative thermal treatment
- 2015
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Ingår i: Nordic Pulp & Paper Research Journal. - : Walter de Gruyter GmbH. - 0283-2631 .- 2000-0669. ; 30:4, s. 550-561
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Tidskriftsartikel (refereegranskat)abstract
- Heat treatment is a promising pre-processing method in the conversion of kraft lignins to carbon fibers. In this study, a kraft lignin was subjected to heat treatment at different lengths of time and at different temperatures. The molecular structure of the untreated and four heat treated lignins were investigated mainly by a variety of nuclear magnetic resonance spectroscopy (NMR) methods. The results were compared to structural information obtained by pyrolysis-gas chromatography-/mass spectrometry (py-GC/MS) and Fourier transform infrared spectroscopy (FTIR). It was observed that during the thermal treatment, the amount of β-O-4 ether moieties decreased, and an intramolecular conversion of secoisolariciresinol residues to cyclic ethers occurred. The effects on shape and size of the lignins were investigated by size exclusion chromatography (SEC) and NMR-diffusion measurements, by which the hydrodynamic radii were found to increase as a result of thermal treatment. It is discussed whether this depends on reduced flexibility and/or increased molar mass. In addition, the trends from the SEC and NMR analyses were compared to changes in glass transition temperature as determined by differential scanning calorimetry (DSC).
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| 12. |
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| 13. |
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| 14. |
- Skedung, Lisa, et al.
(författare)
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Identification and quantification of fluorinated polymers in consumer products by combustion ion chromatography and pyrolysis-gas chromatography-mass spectrometry
- 2024
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Ingår i: Environmental Science. - 2050-7887 .- 2050-7895. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Total fluorine was determined in 45 consumer product samples from the Swedish market which were either suspected or known to contain fluorinated polymers. Product categories included cookware (70–550 000 ppm F), textiles (10–1600 ppm F), electronics (20–2100 ppm F), and personal care products (10–630 000 ppm F). To confirm that the fluorine was organic in nature, and deduce structure, a qualitative pyrolysis-gas chromatography-mass spectrometry (pyr-GC/MS) method was validated using a suite of reference materials. When applied to samples with unknown PFAS content, the method was successful at identifying polytetrafluoroethylene (PTFE) in cookware, dental products, and electronics at concentrations as low as 0.1–0.2 wt%. It was also possible to distinguish between 3 different side-chain fluorinated polymers in textiles. Several products appeared to contain high levels of inorganic fluorine. This is one of the few studies to quantify fluorine in a wide range of consumer plastics and provides important data on the concentration of fluorine in materials which may be intended for recycling, along with insights into the application of pyr-GC/MS for structural elucidation of fluorinated polymers in consumer products.
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