| 1. |
- Barbara Sahlin, K., et al.
(författare)
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Short-term effect of induced alterations in testosterone levels on fasting plasma amino acid levels in healthy young men
- 2021
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Ingår i: Life. - : MDPI AG. - 0024-3019 .- 2075-1729. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Long term effect of testosterone (T) deficiency impairs metabolism and is associated with muscle degradation and metabolic disease. The association seems to have a bidirectional nature and is not well understood. The present study aims to investigate the early and unidirectional metabolic effect of induced T changes by measuring fasting amino acid (AA) levels in a human model, in which short-term T alterations were induced. We designed a human model of 30 healthy young males with pharmacologically induced T changes, which resulted in three time points for blood collection: (A) baseline, (B) low T (3 weeks post administration of gonadotropin releasing hormone antagonist) and (C) restored T (2 weeks after injection of T undecanoate). The influence of T on AAs was analyzed by spectrophotometry on plasma samples. Levels of 9 out of 23 AAs, of which 7 were essential AAs, were significantly increased at low T and are restored upon T supplementation. Levels of tyrosine and phenylalanine were most strongly associated to T changes. Short-term effect of T changes suggests an increased protein breakdown that is restored upon T supplementation. Fasting AA levels are able to monitor the early metabolic changes induced by the T fluctuations.
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| 2. |
- de Siqueira Guedes, Jéssica, et al.
(författare)
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Plasma metabolome study reveals metabolic changes induced by pharmacological castration and testosterone supplementation in healthy young men
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Testosterone is a hormone that plays a key role in carbohydrate, fat, and protein metabolism. Testosterone deficiency is associated with multiple comorbidities, e.g., metabolic syndrome and type 2 diabetes. Despite its importance in many metabolic pathways, the mechanisms by which it controls metabolism are not fully understood. The present study investigated the short-term metabolic changes of pharmacologically induced castration and, subsequently, testosterone supplementation in healthy young males. Thirty subjects were submitted to testosterone depletion (TD) followed by testosterone supplementation (TS). Plasma samples were collected three times corresponding to basal, low, and restored testosterone levels. An untargeted metabolomics study was performed by liquid chromatography–high resolution mass spectrometry (UHPLC–HRMS) to monitor the metabolic changes induced by the altered hormone levels. Our results demonstrated that TD was associated with major metabolic changes partially restored by TS. Carnitine and amino acid metabolism were the metabolic pathways most impacted by variations in testosterone. Furthermore, our results also indicated that LH and FSH might strongly alter the plasma levels of indoles and lipids, especially glycerophospholipids and sphingolipids. Our results demonstrated major metabolic changes induced by low testosterone that may be important for understanding the mechanisms behind the association of testosterone deficiency and its comorbidities.
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| 3. |
- Mavrona, Elena, et al.
(författare)
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Efficiency assessment of wood and cellulose-based optical elements for terahertz waves
- 2023
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Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:1, s. 92-103
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Tidskriftsartikel (refereegranskat)abstract
- Polarized THz time domain spectroscopy was used to study the anisotropic properties of wood-based materials for potential optical elements in the THz range, such as half-wave and quarter-wave plates. Wood samples of different species and sample thickness were studied experimentally showing high birefringence but rather high absorption. We elaborate on two approaches to optimize the optical properties for use as wave plates and assess them based on a figure of merit describing their efficiency as a function of birefringence and absorption. The first approach is to dry the wood samples, which significantly improves the efficiency of wave plates. The second approach is the use of artificially produced cellulose samples using 3D printing and freeze drying techniques, which also show birefringence caused by their similar macroscopic cellulose fibre structure. These materials have the potential as cost effective THz elements that are easy to tailor and produce for use at specific frequencies.
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| 4. |
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| 5. |
- Oksman, Kristiina, et al.
(författare)
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Cellulose nanofiber isolated from industrial side-streams
- 2013
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Ingår i: Production and Applications of Cellulose Nanomaterials. - : TAPPI Press. - 9781595102249 ; , s. 187-190
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Bokkapitel (refereegranskat)abstract
- Isolation of cellulose nanofibers from industrial side-streams as raw material is interesting from several reasons; it will not only result in lower overall cost of the nanofibers but also add value for many different processes and products. We have used sludge, a residue from pulp production, carrot residue from juice production, and several agricultural waste products as the starting material to isolate nanofibers. The isolation process was made using a Masuko ultra fine friction grinder and our aim have been to optimize the processing parameters for the lowest energy consumption. In addition to developing the isolation process, the isolated nanofibers structure and properties were characterized. Typically, the isolated nanofibers are bundles with diameters lower than 100 nm. In particular, we found that carrot nanofibers have a uniform fiber size less than 50 nm. Scanning electron microscopy studies showed entangled nanofiber networks and the mechanical properties of nanofiber networks demonstrated a positive impact on modulus and strength when compared to networks with microsized fibers. The improvement is increased with decreased fiber size indicating more efficient fibrillation. From these studies, we have shown that industrial side-streams are excellent raw material sources for nanofiber preparation, being cheaper than other raw materials and consuming less energy for isolation while showing good properties.
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| 6. |
- Oksman, Kristiina, et al.
(författare)
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Review of the recent developments in cellulose nanocomposite processing
- 2016
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier. - 1359-835X .- 1878-5840. ; 83, s. 2-18
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Forskningsöversikt (refereegranskat)abstract
- This review addresses the recent developments of the, processing of cellulose nanocomposites, focusing on the most used techniques, including solution casting, melt-processing of thermoplastic cellulose nanocomposites and resin impregnation of cellulose nanopapers using thermoset resins. Important techniques, such as partially dissolved cellulose nanocomposites, nanocomposite foams reinforced with nanocellulose, as well as long continuous fibers or filaments, are also addressed. It is shown how the research on cellulose nanocomposites has rapidly increased during the last 10 years, and manufacturing techniques have been developed from simple casting to these more sophisticated methods. To produce cellulose nanocomposites for commercial use, the processing of these materials must be developed from laboratory to industrially viable methods.
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| 7. |
- Pöhler, Tiina, et al.
(författare)
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Pilot-scale modification of polyethersulfone membrane with a size and charge selective nanocellulose layer
- 2022
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Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1383-5866 .- 1873-3794. ; 285
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Tidskriftsartikel (refereegranskat)abstract
- The utilisation of plant-derived nanoscale cellulosic materials (cellulose nanofibrils, CNF) in tailoring water purification membranes is constantly gaining interest in the context of green-functionalised membrane solutions. However, most of the existing approaches based on renewable and biobased materials suffer from the lack of efficient and scalable processing strategies. Here, we introduce a roll-to-roll membrane modification approach based on thin submicron nanocellulose coatings (400–800 nm) to manufacture anti-biofouling membranes with size and charge dependent selectivity using unit operations compatible with existing industrial lines. We turned a commercial polymeric polyethersulfone (PES) microfiltration membrane into highly hydrophilic and tight membrane structure by applying thin and water-durable cellulose nanofibril layers using cast or spray coating methods. Nanocellulose coated membranes exhibited water permeance values of 80 – 100 LMH/MPa with the highest rejection levels of > 90% for Cytochrome C. Furthermore, the nanocellulose layers were able to withstand relatively high filtration pressure levels of 1 MPa, indicating that the selected procedures to improve mechanical integrity i.e. polyethylene imine-based anchoring and acid induced CNF cross-linking were successful. The coated membranes with the thinnest nanocellulose layer exhibited a molecular weight cut-off (MWCO) of 2 kDa for negatively charged polystyrene sulfonate and 14 kDa for neutral dextrane indicating charge selective behaviour. It can be concluded that our nanocellulose coated PES membranes represent nanofiltration membranes and lower boundary of ultrafiltration membranes with clear anti-biofouling performance directly evidenced via systematic bovine serum albumin (BSA) adsorption investigations. Our approach paves the way towards tunable and sustainable water treatment technologies simultaneously opening space for novel biobased solutions in membrane sector.
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| 8. |
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| 9. |
- Siqueira, Gilberto, et al.
(författare)
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Cellulosic bionanocomposites : a review of preparation, properties and applications
- 2010
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 2:4, s. 728-765
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose is the most abundant biomass material in nature. Extracted from natural fibers, its hierarchical and multi-level organization allows different kinds of nanoscaled cellulosic fillers-called cellulose nanocrystals or microfibrillated cellulose (MFC)-to be obtained. Recently, such cellulose nanoparticles have been the focus of an exponentially increasing number of works or reviews devoted to understanding such materials and their applications. Major studies over the last decades have shown that cellulose nanoparticles could be used as fillers to improve mechanical and barrier properties of biocomposites. Their use for industrial packaging is being investigated, with continuous studies to find innovative solutions for efficient and sustainable systems. Processing is more and more important and different systems are detailed in this paper depending on the polymer solubility, i.e., (i) hydrosoluble systems, (ii) non-hydrosoluble systems, and (iii) emulsion systems. This paper intends to give a clear overview of cellulose nanoparticles reinforced composites with more than 150 references by describing their preparation, characterization, properties and applications
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| 10. |
- Siqueira, Gilberto, et al.
(författare)
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Processing of cellulose nanowhiskers/cellulose acetate butyrate nanocomposites using sol-gel process to facilitate dispersion
- 2011
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 71:16, s. 1886-1892
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Tidskriftsartikel (refereegranskat)abstract
- Biobased nanocomposites based on cellulose nanowhiskers (CNWs) and cellulose acetate butyrate (CAB) were prepared using solvent exchange of CNWs to ethanol by sol-gel method followed by casting. The strong flow birefringence of the solutions indicated evenly dispersed cellulose nanowhiskers in the dissolved polymer CAB. Scanning electron microscopy of the nanocomposites confirmed well dispersed CNWs in the CAB matrix, which was further supported by the high transparency exhibited by the nanocomposites. The results of tensile tests indicated significant improvements in the mechanical properties of nanocomposites by increasing the CNWs contents. The Young’s modulus and strength increased 83% and 70%, respectively, for nanocomposites with 12 wt% of CNW, and the strain was not suppressed compared to the neat CAB. The dynamic mechanical thermal analysis demonstrated significant improvement in storage modulus with increasing CNW contents, and the tan δ peak position was moved towards higher temperature when CNW was added. It is expected that solvent exchange by the sol-gel route followed by casting of nanocomposites from the same solvent will provide a promising route for obtaining cellulose nanocomposites with well dispersed CNW, leading to improved mechanical properties, even with low nanowhisker contents.
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