| 1. |
- ANDERSSON, MICHAEL, 1988, et al.
(author)
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Feasibility of Ambient RF Energy Harvesting for Self-Sustainable M2M Communications Using Transparent and Flexible Graphene Antennas
- 2016
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In: IEEE Access. - 2169-3536 .- 2169-3536. ; 4, s. 5850-5857
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Journal article (peer-reviewed)abstract
- Lifetime is a critical parameter in ubiquitous, battery-operated sensors for machine-to-machine (M2M) communication systems, an emerging part of the future Internet of Things. In this practical article, the performance of radio frequency (RF) to DC energy converters using transparent and flexible rectennas based on graphene in an ambient RF energyharvesting scenario is evaluated. Full-wave EM simulations of a dipole antenna assuming the reported state-of-the-art sheet resistance for few-layer, transparent graphene yields an estimated ohmic efficiency of 5 %. In the power budget calculation, the low efficiency of transparent graphene antennas is an issue because of the relatively low amount of available ambient RF energy in the frequency bands of interest, which together sets an upper limit on the harvested energy available for the RF-powered device. Using a commercial diode rectifier and an off-the-shelf wireless system for sensor communication, the graphene-based solution provides only a limited battery lifetime extension. However, for ultra-low-power technologies currently at the research stage, more advantageous ambient energy levels, or other use cases with infrequent data transmission, graphene-based solutions may be more feasible.
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| 2. |
- Linderhed, Ulrika, et al.
(author)
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Fully screen printed stretchable electrochromic displays
- 2021
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In: Flexible and Printed Electronics. - : IOP Publishing Ltd. - 2058-8585. ; 6:4
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Journal article (peer-reviewed)abstract
- The advent of the Internet of Things and the growing interest in continuous monitoring by wearables have created a need for conformable and stretchable displays. Electrochromic displays (ECDs) are receiving attention as a cost-effective solution for many simple applications. However, stretchable ECDs have yet to be produced in a robust, large scale and cost-efficient manner. Here we develop a process for making fully screen printed stretchable ECDs. By evaluating commercially available inks with respect to electromechanical properties, including electrochromic PEDOT:PSS inks, our process can be directly applied in the manufacturing of stretchable organic electronic devices. The manufactured ECDs retained colour contrast with useful switching times at static strains up to 50% and strain cycling up to 30% strain. To further demonstrate the applicability of the technology, double-digit 7-segment ECDs were produced, which could conform to curved surfaces and be mounted onto stretchable fabrics while remaining fully functional. Based on their simplicity, robustness and processability, we believe that low cost printed stretchable ECDs can be easily scaled up and will find many applications within the rapidly growing markets of wearable electronics and the Internet of Things. © 2021 The Author(s).
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| 3. |
- Andersson, Ulrika
(author)
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Beta-glucose 1-phosphate interconverting enzymes in Lactococcus lactis: physiological role and regulation in maltose, trehalose and glucose metabolism
- 2002
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Doctoral thesis (other academic/artistic)abstract
- Lactic acid bacteria (LAB), including Lactococcus lactis, are abundant in nature. These bacteria convert carbohydrates into mainly lactate by a rather uncomplicated metabolism. An improved understanding of the physiological and genetical mechanisms involved in carbohydrate metabolism and its regulation will improve the industrial use of LAB. The aim of this study was to investigate the maltose and trehalose assimilating pathways in L. lactis. The maltose phosphorylase (MP) and beta-phosphoglucomutase (b-PGM) of L. lactis were characterised and shown to constitute the major maltose-degrading pathway in this bacterium. Furthermore, MP and b-PGM were shown to be present in many other strains of LAB belonging to the low G+C content LAB of the clostridial sub-branch of gram-positive bacteria. The MP-encoding gene, malP, was localised in an operon distinctive from that of the gene encoding b-PGM, pgmB. In addition, malR, encoding the maltose operon regulator (MalR), was localised downstream of malP. The presence of MalR was shown to be crucial for the synthesis of an ATP-dependent maltose translocation system. However, MP and b-PGM activity were not affected by a disruption of the MalR-encoding gene. Instead, synthesis of b-PGM has been shown to be exposed to carbon catabolite repression, which was also shown to be the case for MP. pgmB is located in the putative trehalose operon including the genes presumed to code for the trehalose-specific components of the phosphotransferase system transporting trehalose into the cells. Furthermore, directly upstream of pgmB, trePP was localised. This gene was shown to encode a novel phosphorylase, trehalose 6-phosphate phosphorylase (TrePP), catalysing the reversible Pi-dependent phosphorolysis of trehalose 6-phosphate to beta-glucose 1-phosphate and glucose 6-phosphate. TrePP was biochemically characterised and shown to be present in a few other species, mainly Enterococcus faecalis, of low G+C content LAB. The role of b-PGM in trehalose metabolism and in polysaccharide synthesis was assessed by disrupting its encoding gene. b-PGM was shown to be crucial for trehalose assimilation in L. lactis, while the b-PGM-deficient strain continued to grow with a tenfold decreased growth rate on maltose, compared to the wild-type strain. The b-PGM-deficient strain showed an enhanced production of polysaccharide, composed of alpha-1,4-linked glucose units when cultivated on maltose. It was suggested that this polysaccharide was a result from another metabolic pathway, resembling the maltodextrin system in Escherichia coli. Global regulatory circuits play a notable role when cells are adapting to environmental changes. A L. lactis mutant, TMB5003, was obtained by an unknown genetic event in the wild-type strain 19435. TMB5003 possessed an enhanced growth rate in glucose batch culture and a 1.5 times higher specific lactate productivity under non-limiting glucose conditions, compared to 19435. TMB5003 transported glucose by a non-saturating mode and the lactate dehydrogenase activity was twenty times higher in this strain compared to 19435. In conclusion, the results obtained for TMB5003, together with the characterisation of the initial disaccharide metabolism in L. lactis, may lead to improved industrial lactate production from LAB.
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| 4. |
- Andersson, Ulrika, et al.
(author)
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Physiological function of the maltose operon regulator, MalR, in Lactococcus lactis.
- 2002
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In: BMC Microbiology. - 1471-2180. ; 2
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Journal article (peer-reviewed)abstract
- BACKGROUND: Maltose metabolism is initiated by an ATP-dependent permease system in Lactococcus lactis. The subsequent degradation of intracellular maltose is performed by the concerted action of Pi-dependent maltose phosphorylase and beta-phosphoglucomutase. In some Gram-positive bacteria, maltose metabolism is regulated by a maltose operon regulator (MalR), belonging to the LacI-GalR family of transcriptional regulators. A gene presumed to encode MalR has been found directly downstream the maltose phosphorylase-encoding gene, malP in L. lactis. The purpose of this study was to investigate the physiological role of the MalR protein in maltose metabolism in L. lactis. RESULTS: A L. lactis ssp. lactis mutant, TMB5004, deficient in the putative MalR protein, was physiologically characterised. The mutant was not able to ferment maltose, while its capability to grow on glucose as well as trehalose was not affected. The activity of maltose phosphorylase and beta-phosphoglucomutase was not affected in the mutant. However, the specific maltose uptake rate in the wild type was, at its lowest, five times higher than in the mutant. This difference in maltose uptake increased as the maltose concentration in the assay was increased. CONCLUSION: According to amino acid sequence similarities, the presumed MalR is a member of the LacI-GalR family of transcriptional regulators. Due to the suggested activating effect on maltose transport and absence of effect on the activities of maltose phosphorylase and beta-phosphoglucomutase, MalR of L. lactis is considered rather as an activator than a repressor.
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| 5. |
- Andersson, Ulrika, et al.
(author)
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Unity in organisation and regulation of catabolic operons in Lactobacillus plantarum, Lactococcus lactis and Listeria monocytogenes
- 2005
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In: Systematic and Applied Microbiology. - : Elsevier BV. - 0723-2020. ; 28:3, s. 187-195
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Journal article (peer-reviewed)abstract
- Global regulatory circuits together with more specific local regulators play a notable role when cells are adapting to environmental changes. Lactococcus lactis is a lactic acid bacterium abundant in nature fermenting most mono- and disaccharides. Comparative genomics analysis of the operons encoding the proteins and enzymes crucial for catabolism of lactose, maltose and threhalose revealed an obvious unity in operon organisation. The local regulator of each operon was located in a divergent transcriptional direction to the rest of the operon including the transport protein-encoding genes. Furthermore, in all three operons a catabolite responsive element (CRE) site was detected inbetween the gene encoding the local regulator and one of the genes encoding ! sugar transport protein. It is evident that regardless of type of transport system and catabolic enzymes acting upon lactose, maltose and trehalose, respectively, Lc. lactis shows unity in both operon organisation and regulation of these catabolic operons. This knowledge was further extended to other catabolic operons in Lc. lactis and the two related bacteria Lactobacillus plantarum and Listeria monocytogenes. Thirty-nine catabolic operons responsible for degradation of sugars and sugar alcohols in Lc. lactis, Lb. plantarum and L. monocytogenes were investigated and the majority of those possessed the same organisation as the lactose, maltose and trehalose operons of Lc. lactis. Though, the frequency of CRE sites and their location varied among the bacteria. Both Lc. lactis and Lb. plantarum showed CRE sites in direct proximity to genes coding for proteins responsible for sugar uptake. However, in, L. monocytogenes CRE sites were not frequently found and not in the vicinity of genes encoding transport proteins, suggesting a more local mode of regulation of the catabolic operons found and/or the use of inducer control in this bacterium. © 2004 Elsevier GrnbH. All rights reserved.
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| 6. |
- Oluoch, Kevin, et al.
(author)
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Hydrogen peroxide degradation by immobilized cells of alkaliphilic Bacillus halodurans
- 2006
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In: Biocatalysis and Biotransformation. - : Informa UK Limited. - 1024-2422 .- 1029-2446. ; 24:3, s. 215-222
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Journal article (peer-reviewed)abstract
- Whole cells of Bacillus halodurans LBK 261 were used as a source of catalase for degradation of hydrogen peroxide. The organism, B. halodurans grown at 55 degrees C and pH 10, yielded a maximum catalase activity of 275U g(-1) (wet wt.) cells. The catalase in the whole cells was active over a broad range of pH with a maximum at pH8-9. The enzyme was optimally active at 55 degrees C, but had low stability above 40 degrees C. The whole cell biocatalyst exhibited a K m of 6.6mM for H2O2 and V max of 707mM H2O2 min(-1) g(-1) wet wt. cells, and showed saturation kinetics at 50mM H2O2 . The cells were entrapped in calcium alginate and used for H2O2 degradation at pH 9 in batch and continuous mode. In the batch process, the immobilized preparation containing 1.5g (wet wt.) cells could be recycled at least four times for complete degradation of the peroxide in 50mL solution at 25 degrees C. An excess of immobilized biocatalyst could be used in a continuous stirred tank reactor for an average of 9 days at temperatures upto 55 degrees C, and in a packed bed reactor (PBR) for 5days before the beads started to deform.
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| 7. |
-
Sprickor i fasaden
- 2018
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Editorial collection (other academic/artistic)abstract
- Det råder på sina håll en oro och ett mörker i dagens Sverige. Några grupper ser en värld av kollapsande system och spruckna fasader, där folkvalda fattar beslut som utarmar människors trygghet och livsvillkor. Andra ser hur antide-mokratiska krafter, likt början av förra seklet, växer sig allt större och på sina håll ges legitimitet av världsledare. Somliga går så långt som att tala om en demokrati i kris, om obönhörligt växande sprickbildningar i samhällsbygget i spåren av vilka otrygghetens och rädslans landskap breder ut sig. Sprickor i fasaden knyter an till denna rådande debatt och föreställningar om samhällets tillstånd.Världen som vi en gång kände den tycks långsamt glida ur våra händer. Den välputsade fasaden spricker. Eller gör den det? Kanske skiftar samhällets palett i långt fler nyanser än mörkaste grått? Kanske spirar det rent av en värld med allt godare möjligheter för människor att leva och utvecklas? För i kontrast till bilden av samhällets rämnande grundvalar, kan också skymtas skiftningar i värdegrunden i riktning mot ökad tolerans, öppenhet och jämlikhet. Måhända är dessa skiftningar tecken på sprickor också i föreställningen om den spruck-na fasaden? Sprickor i fasaden är den 72:e forskarantologin från SOM-institutet och bygger på 2017 års nationella SOM-undersökning – den trettioandra i ordningen. Bokens innehåll knyter på många sätt an till frågan om sprickor i det svenska samhällsbygget. Flera kapitel belyser tilltagande polarisering och politisering inom (S)amhälle, (O)pinion och (M)edier. Samtidigt pekar resultaten i andra kapitel på en påtaglig stabilitet och förstärkt uppslutning kring centrala värde-ringar, samhällsfrågor och samhällsinstitutioner.Sprickor i fasaden är skriven av ett 30-tal forskare från olika discipliner vid universitet och högskolor i Sverige.
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| 8. |
- Andersson, Christian, et al.
(author)
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Effect of different carbon sources on the production of succinic acid using metabolically engineered Escherichia coli
- 2007
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In: Biotechnology progress (Print). - : Wiley. - 8756-7938 .- 1520-6033. ; 23:2, s. 381-388
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Journal article (peer-reviewed)abstract
- Succinic acid (SA) is an important platform molecule in the synthesis of a number of commodity and specialty chemicals. In the present work, dual-phase batch fermentations with the E. coli strain AFP184 were performed using a medium suited for large-scale industrial production of SA. The ability of the strain to ferment different sugars was investigated. The sugars studied were sucrose, glucose, fructose, xylose, and equal mixtures of glucose and fructose and glucose and xylose at a total initial sugar concentration of 100 g L-1. AFP184 was able to utilize all sugars and sugar combinations except sucrose for biomass generation and succinate production. For sucrose as a substrate no succinic acid was produced and none of the sucrose was metabolized. The succinic acid yield from glucose (0.83 g succinic acid per gram glucose consumed anaerobically) was higher than the yield from fructose (0.66 g g-1). When using xylose as a carbon source, a yield of 0.50 g g-1 was obtained. In the mixed-sugar fermentations no catabolite repression was detected. Mixtures of glucose and xylose resulted in higher yields (0.60 g g-1) than use of xylose alone. Fermenting glucose mixed with fructose gave a lower yield (0.58 g g-1) than fructose used as the sole carbon source. The reason is an increased pyruvate production. The pyruvate concentration decreased later in the fermentation. Final succinic acid concentrations were in the range of 25-40 g L-1. Acetic and pyruvic acid were the only other products detected and accumulated to concentrations of 2.7-6.7 and 0-2.7 g L-1. Production of succinic acid decreased when organic acid concentrations reached approximately 30 g L-1. This study demonstrates that E. coli strain AFP184 is able to produce succinic acid in a low cost medium from a variety of sugars with only small amounts of byproducts formed.
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| 9. |
- Andersson, Christian, et al.
(author)
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Effects of neutralising agent, organic acids, and osmolarity on succinic acid production by Escherichia coli AFP184
- 2008
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Conference paper (other academic/artistic)abstract
- Using a low-cost medium Escherichia coli AFP184 has previously been reported to produce succinic acid with volumetric productivities close to 3 g L-1 h-1. At a total organic acid concentration of 30 g L-1 the productivity decreased drastically resulting in final succinate concentrations of 40 g L-1. The economical viability of biochemical succinic acid production would benefit from higher final succinic acid concentrations and volumetric productivities maintained at >2.5 g L-1 h-1 for an extended period of time. In the present work the effects of osmolarity and neutralising agent (NH4OH, KOH, NaOH, K2CO3, and Na2CO3) on succinic acid production by AFP184 were investigated. Highest concentration of succinic acid was obtained with Na2CO3, 75 g L-1. It was also found that the osmolarity resulting from succinate production and subsequent base addition, only marginally affected the productivity per viable cell. Organic acid inhibition due to the produced succinic acid on the other hand significantly reduced succinic acid productivity per viable cell. When using NH4OH productivity completely ceased at approximately 40 g L-1. Volumetric productivities remained at 2.5 g L-1 h-1 for 5 to 10 hours longer when using K- or Na-bases than when using NH4OH. However, loss of cell viability occurred, and together with the acid inhibition decreased the volumetric productivities. In this study it was demonstrated that by altering the neutralising agent it was possible to increase the period of high volumetric productivity in the anaerobic phase and improve the final succinic acid concentration by almost 100 %
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| 10. |
- Andersson, Christian, et al.
(author)
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Inhibition of succinic acid production in metabolically engineered Escherichia Coli by neutralizing agent, organic acids, and osmolarity
- 2009
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In: Biotechnology progress (Print). - : Wiley. - 8756-7938 .- 1520-6033. ; 25:1, s. 116-123
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Journal article (peer-reviewed)abstract
- The economical viability of biochemical succinic acid production is a result of many processing parameters including final succinic acid concentration, recovery of succinate, and the volumetric productivity. Maintaining volumetric productivities >2.5 g L-1 h(-1) is important if production of succinic acid from. renewable resources should be competitive. In this work, the effects of organic acids, osmolarity, and neutralizing agent (NH4OH, KOH, NaOH, K2CO3, and Na2CO3) on the fermentative succinic acid production by Escherichia coli AFP184 were investigated. The highest concentration of succinic acid, 77 g L-1. was obtained with Na2O3. In general, irrespective of the base used, succinic acid productivity per viable cell was significantly reduced as the concentration of the produced acid increased. Increased osmolarity resulting from base addition during succinate production only marginally affected the productivity per viable cell. Addition of the osmoprotectant glycine betaine to cultures resulted in an increased aerobic growth rate and anaerobic glucose consumption rate, but decreased succinic acid yield. When using NH4OH productivity completely ceased at a succinic acid concentration of similar to 40 g L-1. Volumetric productivities remained at 2.5 g L-1 h(-1) for tip to 10 h longer when K- or Na-bases where used instead of NH4OH. The decrease in cellular succinic acid productivity observed during the anaerobic phase was found to be due to increased organic acid concentrations rather than medium osmolarity.
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