| 1. |
- Aguilar, J., et al.
(författare)
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Search for Leptonic CP Violation with the ESSnuSBplus Project
- 2024
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Ingår i: Letters in High Energy Physics. - : Andromeda Publishing And Academic Services LTD. - 2632-2714.
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Tidskriftsartikel (refereegranskat)abstract
- ESSνSB is a design study for a next-generation long-baseline neutrino experiment that aims at the precise measurement of the CP-violating phase, δCP, in the leptonic sector at the second oscillation maximum. The conceptual design report published from the first phase of the project showed that after 10 years of data taking, more than 70% of the possible δCP range will be covered with 5σ C.L. to reject the no-CP-violation hypothesis. The expected value of δCP precision is smaller than 8◦ for all δCP values. The next phase of the project, the ESSνSB+, aims at using the intense muon flux produced together with neutrinos to measure the neutrino-nucleus cross-section, the dominant term of the systematic uncertainty, in the energy range of 0.2–0.6 GeV, using a Low Energy neutrinos from STORed Muons (LEnuSTORM) and a Low Energy Monitored Neutrino Beam (LEMNB) facilities.
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| 2. |
- Maksimovic, M., et al.
(författare)
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The Solar Orbiter Radio and Plasma Waves (RPW) instrument
- 2020
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Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 642
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Tidskriftsartikel (refereegranskat)abstract
- The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is described in this paper. This instrument is designed to measure in-situ magnetic and electric fields and waves from the continuous to a few hundreds of kHz. RPW will also observe solar radio emissions up to 16 MHz. The RPW instrument is of primary importance to the Solar Orbiter mission and science requirements since it is essential to answer three of the four mission overarching science objectives. In addition RPW will exchange on-board data with the other in-situ instruments in order to process algorithms for interplanetary shocks and type III langmuir waves detections.
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| 3. |
- Maksimovic, M., et al.
(författare)
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First observations and performance of the RPW instrument on board the Solar Orbiter mission
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 656
-
Tidskriftsartikel (refereegranskat)abstract
- The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is designed to measure in situ magnetic and electric fields and waves from the continuum up to several hundred kHz. The RPW also observes solar and heliospheric radio emissions up to 16 MHz. It was switched on and its antennae were successfully deployed two days after the launch of Solar Orbiter on February 10, 2020. Since then, the instrument has acquired enough data to make it possible to assess its performance and the electromagnetic disturbances it experiences. In this article, we assess its scientific performance and present the first RPW observations. In particular, we focus on a statistical analysis of the first observations of interplanetary dust by the instrument's Thermal Noise Receiver. We also review the electro-magnetic disturbances that RPW suffers, especially those which potential users of the instrument data should be aware of before starting their research work.
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| 4. |
- Edberg, Niklas J. T., et al.
(författare)
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Spatial distribution of low-energy plasma around comet 67P/CG from Rosetta measurements
- 2015
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 42:11, s. 4263-4269
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Tidskriftsartikel (refereegranskat)abstract
- We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be approximate to 1-210(-6), at a cometocentric distance of 10km and at 3.1AU from the Sun. A clear 6.2h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260km from the nucleus falls off with radial distance as approximate to 1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet.
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| 5. |
- Andersson, Mats X., 1977, et al.
(författare)
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Involvement of the Electrophilic Isothiocyanate Sulforaphane in Arabidopsis Local Defense Responses
- 2015
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 167:1
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Tidskriftsartikel (refereegranskat)abstract
- Plants defend themselves against microbial pathogens through a range of highly sophisticated and integrated molecular systems. Recognition of pathogen-secreted effector proteins often triggers the hypersensitive response (HR), a complex multicellular defense reaction where programmed cell death of cells surrounding the primary site of infection is a prominent feature. Even though the HR was described almost a century ago, cell-to-cell factors acting at the local level generating the full defense reaction have remained obscure. In this study, we sought to identify diffusible molecules produced during the HR that could induce cell death in naive tissue. We found that 4-methylsulfinylbutyl isothiocyanate (sulforaphane) is released by Arabidopsis (Arabidopsis thaliana) leaf tissue undergoing the HR and that this compound induces cell death as well as primes defense in naive tissue. Two different mutants impaired in the pathogen-induced accumulation of sulforaphane displayed attenuated programmed cell death upon bacterial and oomycete effector recognition as well as decreased resistance to several isolates of the plant pathogen Hyaloperonospora arabidopsidis. Treatment with sulforaphane provided protection against a virulent H. arabidopsidis isolate. Glucosinolate breakdown products are recognized as antifeeding compounds toward insects and recently also as intracellular signaling and bacteriostatic molecules in Arabidopsis. The data presented here indicate that these compounds also trigger local defense responses in Arabidopsis tissue.
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| 6. |
- Brett, Calvin J., et al.
(författare)
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Revealing structural evolution occurring from photo-initiated polymer network formation
- 2020
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Ingår i: Communications Chemistry. - : Springer Science and Business Media LLC. - 2399-3669. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Photopolymerization is a key enabling technology offering spatial and temporal control to allow for future functional materials to be made to meet societal needs. However, gaining access to robust experimental techniques to describe the evolution of nanoscale morphology in photo-initiated polymeric systems has proven so far to be a challenging task. Here, we show that these physical transformations can be monitored and quantified at the nanoscale in situ and in real-time. It is demonstrated that the initial structural features of the liquid precursors significantly affect the final morphology and the physical properties of the resulting solid via the occurrence of local heterogeneities in the molecular mobility during the curing transformation. We have made visible how local physical arrestings in the liquid, associated with both cross-linking and vitrification, determine the length scale of the local heterogeneities forming upon curing, found to be in the 10-200nm range. Acomplete account of the structural evolution occurring during photopolymerisation is lacking. Here the physical changes occurring on the nanometer scale during photopolymerisation of acrylates are followed over time by FTIR, X-ray reflectometry, AFM, and GISAXS, offering insight into the mechanism by which initial composition influences the final morphology.
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| 7. |
- Edberg, Niklas J. T., et al.
(författare)
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CME impact on comet 67P/Churyumov-Gerasimenko
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462, s. S45-S56
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Tidskriftsartikel (refereegranskat)abstract
- We present Rosetta observations from comet 67P/Churyumov-Gerasimenko during the impact of a coronal mass ejection (CME). The CME impacted on 2015 Oct 5-6, when Rosetta was about 800 km from the comet nucleus, and 1.4 au from the Sun. Upon impact, the plasma environment is compressed to the level that solar wind ions, not seen a few days earlier when at 1500 km, now reach Rosetta. In response to the compression, the flux of suprathermal electrons increases by a factor of 5-10 and the background magnetic field strength increases by a factor of similar to 2.5. The plasma density increases by a factor of 10 and reaches 600 cm(-3), due to increased particle impact ionization, charge exchange and the adiabatic compression of the plasma environment. We also observe unprecedentedly large magnetic field spikes at 800 km, reaching above 200 nT, which are interpreted as magnetic flux ropes. We suggest that these could possibly be formed by magnetic reconnection processes in the coma as the magnetic field across the CME changes polarity, or as a consequence of strong shears causing Kelvin-Helmholtz instabilities in the plasma flow. Due to the limited orbit of Rosetta, we are not able to observe if a tail disconnection occurs during the CME impact, which could be expected based on previous remote observations of other CME-comet interactions.
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| 8. |
- Ansari, Farhan, et al.
(författare)
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Cellulose nanofiber network for moisture stable, strong and ductile biocomposites and increased epoxy curing rate
- 2014
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Ingår i: Composites. Part A, Applied science and manufacturing. - : Elsevier BV. - 1359-835X .- 1878-5840. ; 63, s. 35-44
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites with high volume fractions (15-50 vol%) of nanofibrillated cellulose (NFC) were prepared by impregnation of a wet porous NFC network with acetone/epoxy/amine solution. Infrared spectroscopy studies revealed a significant increase in curing rate of epoxy (EP) in the presence of NFC. The NFC provided extremely efficient reinforcement (at 15 vol%: 3-fold increase in stiffness and strength to 5.9 GPa and 109 MPa, respectively), and ductility was preserved. Besides, the glass transition temperature increased with increasing NFC content (from 68 degrees C in neat epoxy to 86 degrees C in 50 vol% composite). Most interestingly, the moisture sorption values were low and even comparable to neat epoxy for the 15 vol% NFC/EP. This material did not change mechanical properties at increased relative humidity (90% RH). Thus, NFC/EP provides a unique combination of high strength, modulus, ductility, and moisture stability for a cellulose-based biocomposite. Effects from nanostructural and interfacial tailoring are discussed.
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| 9. |
- Claudino, Mauro, et al.
(författare)
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Bringing D-limonene to the scene of bio-based thermoset coatings via free-radical thiol-ene chemistry : macromonomer synthesis, UV-curing and thermo-mechanical characterization
- 2014
-
Ingår i: Polymer Chemistry. - : Royal Society of Chemistry (RSC). - 1759-9954. ; 5:9, s. 3245-3260
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Tidskriftsartikel (refereegranskat)abstract
- The increasing pursuit for bio-based plastic materials led us to investigate the potential use of the monoterpene limonene in thermoset synthesis using the free-radical mediated thiol-ene reaction. The high efficiency of this reaction to prepare multifunctional ene-terminated resins, as intermediary macromolecular precursors, for thermosets synthesis was demonstrated under thermal and photoinitiated conditions. Although an excess of terpene favors formation of well-defined macromonomers in organic solution, the characteristic low-vapor pressure of limonene hinders its simple removal (or recycling) via evaporation after synthesis. Alteration to an initial thiol-ene stoichiometry of 1 : 0.5 enables production of high molecular weight resins in the form of 'hyperbranched oligomeric-like' structures having moderate polydispersity. UV-curing of these polyfunctional resins combined with equal mole compositions of multifunctional alkyl ester 3-mercapto propionates yields highly sticky, amorphous and flexible elastomers with different thermo-mechanical properties. These can be further modulated by varying the amount of unreacted thiol occluded within the networks working as a plasticizer. Introduction of a renewable cycloaliphatic structure into the materials offers a convenient way to enhance the glass-transition temperature and stiffness of traditional thiol-ene networks. The materials synthesized may be considered potentially useful as sealants and adhesives in a wide variety of applications including organic coatings. The versatility of UV-irradiation over thermal initiation makes this method particularly suitable for green industrial synthesis processes via thiol-ene chemistry using limonene and multifunctional thiols. The thiol-ene system evaluated herein serves as a model example for the sustainable incorporation of natural diolefinic monomers into semisynthetic thiol-ene networks exhibiting a range of thermo-mechanical properties.
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| 10. |
- Claudino, Mauro, et al.
(författare)
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Photoinduced thiol-ene cross-linking of globalide/ε-caprolactone copolymers : curing performance and resulting thermoset properties
- 2012
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 50:1, s. 16-24
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demand for bioderived polymers led us to investigate the potential use of the macrolactone globalide in thermoset synthesis via the photoinduced thiolene reaction. A series of six lipase-catalyzed poly(globalide-caprolactone) copolyesters bearing internal main-chain unsaturations ranging from 10 to 50 and 100 mol % were successfully crosslinked in the melt with equal amounts of thiol groups from trimethylolpropane-trimercapto propionate affording fully transparent amorphous elastomeric materials with different thermal and viscoelastic properties. Three major conclusions can be drawn from this study: (i) high thiol-ene conversions (> 80%) were easily attained for all cases, while maintaining the cure behavior, and irrespective of functionality at reasonable reaction rates; (ii) parallel chain-growth homopropagation of the ene monomer is insignificant when compared with the main thiolene coupling route; and (iii) high ene-density copolymers result in much lower extracted sol fractions and high T(g) values as a result of a more dense and homogeneous crosslinked network. The thiol-ene system evaluated in this contribution serve as model example for the sustainable use of naturally occurring 1,2-disubstituted alkenes in making semisynthetic polymeric materials in high conversions with a range of properties.
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| 11. |
- Claudino, Mauro, et al.
(författare)
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Thiol-ene coupling of 1,2-disubstituted alkene monomers : The kinetic effect of cis/trans-isomer structures
- 2010
-
Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 46:12, s. 2321-2332
-
Tidskriftsartikel (refereegranskat)abstract
- The free-radical induced reaction between a tri-functional thiol (2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto propionate) and two 1,2-disubstituted alkenes (methyl oleate and methyl elaidate) has been investigated under photochemical conditions. The photoreaction was monitored via time-resolved FUR, Raman and NMR spectroscopy to provide insights about the kinetics and efficiency in end-product formation. The information collected was subjected to numerical modelling using the GEPASI software using pre-established literature values for the rate coefficients in order to verify the proposed reaction scheme. The results confirm the thiol-ene reaction mechanism showing a very fast cis/trans-isomerization (<1.0 min) when compared with the total disappearance of unsaturations, indicating that the rate-limiting step controlling the reaction is the hydrogen transfer from the thiol involved in the formation of product. High thiol-ene conversions can be obtained at reasonable rates without major influence of side-reactions when performed in bulk indicating that this reaction is suitable for network forming purposes with mono-unsaturated fatty acid methyl esters derivatives. The kinetic and mechanistic information collected provides a basis for the design of new thiol-ene systems aiming at material and coating applications.
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| 12. |
- Claudino, Mauro
(författare)
-
Thiol−ene Coupling of Renewable Monomers : at the forefront of bio-based polymeric materials
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Plant derived oils bear intrinsic double-bond functionality that can be utilized directly for the thiol–ene reaction. Although terminal unsaturations are far more reactive than internal ones, studies on the reversible addition of thiyl radicals to 1,2-disubstituted alkenes show that this is an important reaction. To investigate the thiol–ene coupling reaction involving these enes, stoichiometric mixtures of a trifunctional propionate thiol with monounsaturated fatty acid methyl esters (methyl oleate or methyl elaidate) supplemented with 2.0 wt.% Irgacure 184 were subjected to 365-nm UV-irradiation and the chemical changes monitored. Continuous (RT– FTIR) and discontinuous (NMR and FT–Raman) techniques were used to follow the progress of the reaction and reveal details of the products formed. Experimental results supported by numerical kinetic simulations of the system confirm the reaction mechanism showing a very fast cis/trans-isomerization of the alkene monomers (<1.0 min) when compared to the total disappearance of double-bonds, indicating that the rate-limiting step controlling the overall reaction is the hydrogen transfer from the thiol involved in the formation of final product. The loss of total unsaturations equals thiol consumption throughout the entire reaction; although product formation is strongly favoured directly from the trans-ene. This indicates that initial cis/trans-isomer structures affect the kinetics. High thiol–ene conversions could be easily obtained at reasonable rates without major influence of side-reactions demonstrating the suitability of this reaction for network forming purposes from 1,2-disubstituted alkenes. To further illustrate the validity of this concept in the formation of cross-linked thiol–ene films a series of globalide/caprolactone based copolyesters differing in degree of unsaturations along the backbone were photopolymerized in the melt with the same trithiol giving amorphous elastomeric materials with different thermal and viscoelastic properties. High thiol–ene conversions (>80%) were easily attained for all cases at reasonable reaction rates, while maintaining the cure behaviour and independent of functionality. Parallel chain-growth ene homopolymerization was considered negligible when compared with the main coupling route. However, the comonomer feed ratio had impact on the thermoset properties with high ene-density copolymers giving networks with higher glass transition temperature values (Tg) and a narrower distribution of cross-links than films with lower ene composition. The thiol–ene systems evaluated in this study serve as model example for the sustainable use of naturally-occurring 1,2-disubstituted alkenes at making semi-synthetic polymeric materials in high conversions with a range of properties in an environment-friendly way.
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| 13. |
- Finnveden, Maja, et al.
(författare)
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One-Component Thiol-Alkene Functional Oligoester Resins Utilizing Lipase Catalysis
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935.
-
Tidskriftsartikel (refereegranskat)abstract
- Chemo-enzymatic methods are powerful tools for the synthesis of novel materials. By combining the flexibility of chemical synthesis and the high selectivity of enzymes, a variety of functional materials can be achieved. In the present study, a series of α,ω-thiol telechelic oligoesters with varying amount of internal alkenes are prepared using selective lipase catalysis and are subsequently cross-linked by thiol-ene chemistry yielding alkene functional networks. Due to the reactivity of thiols and alkenes almost all present thiol-ene systems consist of two components. This work demonstrates that selective lipase catalysis in combination with renewable monomers with internal alkenes is a promising system for achieving one-component thiol-alkene functional resins with good storage stability and a high degree of thiol end-groups. The developed chemo-enzymatic route yields polymer networks with tailored amount of alkene functionalities in the final thermoset, which facilitate further postmodification.
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| 14. |
- Johansson, C. -G, et al.
(författare)
-
Exhaust noise - A new novel in-situ measurement technology in duct
- 2005
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Ingår i: 12th International Congress on Sound and Vibration 2005. - 9781627481496 ; , s. 1639-1648
-
Konferensbidrag (refereegranskat)abstract
- The noise emission from large internal combustion engines, from 500 kW to 20 MW, is inherently difficult to predict with a high degree of confidence. How the actual noise field propagates within a complex exhaust gas system and how to measure exhaust noise where the gas flow in the duct could be as high as 40 m/s and temperature about 350 degree. This translates to increased cost for silencer over-sizing or added costs associated with an exhaust gas system that fails to meet the required noise signature. This paper deals with a new and verified hot gas (< 600 C) in-situ noise measurement technology called SESaM. It makes it possible to accurately measure source strength and specific insertion loss of the various components in the exhaust train behind large 2 or 4 stroke diesels and power plant gas turbine, also under field conditions. When designing an exhaust system for diesel engine it is most important to have a correct source spectrum for the engine and the noise requirement raised by the final customer in order to do the precision design for the attenuation in the system. In the past the source spectrum of diesel engines always has been an issue of large uncertainty due to the fact that no general reliable measurement procedure exists. The paper presents the practical induct SESaM technology and discusses measurement results versus the time consuming and less accurate classic method.
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| 15. |
- Johansson, Katarina, et al.
(författare)
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A Model Study on Fatty Acid Methyl Esters as Reactive Diluents in Thermally Cured Coil Coating Systems
- 2006
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 55:4, s. 382-387
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Tidskriftsartikel (refereegranskat)abstract
- A model study on the transesterification reaction between fatty acid methyl ester (FAME), e.g. methyl oleate, methyl linoleate, rape seed methyl ester and different alcohols in thin films have been performed. The purpose was to evaluate the possibility to use fatty acid methyl ester (FAME) as reactive diluent in thermally cured coil-coating paints. A reactive diluent must be compatible, act as a diluent, react into the film without affecting the end properties. The transesterification between the methyl ester and hydroxyl functional model compounds was monitored by 1H-NMR and real time IR. The effects addressed in the present study were compatibility, temperature, catalyst, alcohol structure, and fatty acid methyl ester (FAME) structure. Competing factors with the transesterification reaction were shown to be evaporation and side reactions i.e. oxidation. The structure of the fatty acid methyl ester (FAME) affects the conversion as a higher amount of unsaturations triggers the competing side reaction oxidation. The reaction time and temperature affects both the degree of transesterification conversion, degree of side reactions and the catalyst choice. The present study has shown that a fatty acid methyl ester (FAME) fulfils the reactivity part for a reactive diluent in a thermally cured coating system.
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| 16. |
- Johansson, Katarina, et al.
(författare)
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Fatty Acid Methyl Ester as Reactive Diluent in Thermally Cured Solvent-Borne Coil-Coatings : The Effect of Fatty Acid Pattern on the Curing Performance and Final Properties
- 2008
-
Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 63:2, s. 155-159
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Tidskriftsartikel (refereegranskat)abstract
- Four different fatty acid methyl esters (FAMEs): rape seedmethyl ester (RME), tall oil methyl ester (TOME), and two types of linseed oilmethyl ester (Linutin) have been studied as reactive diluents in thermally cured solvent-borne coil-coatings. The purpose was to evaluate the effect of fatty acid methyl ester structure on the curing performance and final properties of the coating. The permanent incorporation of the reactive diluent via transesterification reaction has been followed with 1H NMR analysis of model systems. Dynamic mechanical analysis (DMA) measurements, of free-standing films, showthat the glass transition temperature (Tg) decreases upon addition of the reactive diluent. Both the amount of incorporated reactive diluent and the final film properties are affected by the number and placement of alkene-bonds in the FAME.
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| 17. |
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| 18. |
- Johansson, Katarina, et al.
(författare)
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Hyperbranched Aliphatic Polyesters and Reactive Diluents in Thermally Cured Coil Coatings
- 2009
-
Ingår i: ACS Applied Materials & Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 1:1, s. 211-217
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Tidskriftsartikel (refereegranskat)abstract
- Two hydroxy-functional hyperbranched aliphatic polyesters based on 2,2-dimethylolpropionic acid (bis-MPA) and a partially aromatic conventional polyester have been studied as thermoset resins for solvent-borne thermally cured polyester crosslinked with melamine coatings for precoated sheet metal, i.e., coil coatings. The hyperbranched polyesters differ with respect to the ratio of the end groups, being either hydroxyls or alkyl esters. The rheological properties of formulations with different polyester resin composition and reactive diluent, Le., rape seed methyl ester, content have been evaluated with viscosity measurements. Films cured either under industrial cure conditions to obtain a peak metal temperature of 232-241 degrees C or at a lower temperature, i.e., 130 degrees C, on untreated or organic primer-coated hot-dipped-galvanized steel substrates have been prepared. The film properties have been evaluated with differential scanning calorimetry and conventional film characterization techniques, i.e., adhesion, impact, Erichsen cupping, pencil hardness, microhardness, and scratch and chemical resistance tests. Formulations possessing high drying ability with maintained suitable film application viscosity were obtained using a hyperbranched polyester resin and a reactive diluent. It is proposed that a solvent-free polyester/melamine formulation with sufficient film properties to withstand the rough forming procedures associated with coil coatings can be obtained by further modification of the resin and greater amounts of reactive diluent.
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| 19. |
- Johansson, Katarina, et al.
(författare)
-
Hyperbranched Aliphatic Polyesters as Thermoset Resins for Thermally Cured Coil-Coatings
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Two hydroxy-functional hyperbranched aliphatic polyesters based on 2,2-dimethylol propionic acid (bis-MPA) and a partially aromatic conventional polyester have been studied as thermoset resins for solvent-borne thermally cured polyester cross-linked with melamine coatings for pre-coated sheet metal, i.e. coil-coatings. The hyperbranched polyesters differ with respect to ratio of the end-groups being either hydroxyls or alkyl esters. The rheological properties of formulations with different polyester resin composition and reactive diluent, i.e. rape seed methyl ester (RME), content have been evaluated with viscosity measurements. Films cured either under industrial cure conditions to obtain a peak metal temperature (PMT) of 232-241°C or at a lower temperature, i.e. 130°C, on untreated or organic primer coated hot dipped galvanized (HDG) steel substrates have been prepared. The film properties have been evaluated with differential scanning calorimetry (DSC), and conventional film characterization techniques i.e. adhesion, impact, Erichsen cupping, pencil hardness, micro hardness, scratch and chemical resistance tests. Formulations possessing high drying ability with maintained suitable film application viscosity were obtained using a hyperbranched polyester resin and a reactive diluent. It is proposed that a solvent-free polyester/melamine formulation with sufficient film properties to withstand the rough forming procedures associated with coil-coatings can be obtained by further modification of the resin and greater amounts of reactive diluent.
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| 20. |
- Johansson, Katarina, et al.
(författare)
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The Effect of Fatty Acid Methyl Esters on the Curing Performance and Final Properties of Thermally Cured Solvent-Borne Coil Coatings
- 2007
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Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 59:2, s. 146-151
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Tidskriftsartikel (refereegranskat)abstract
- The solvent content of a thermally cured coil-coating paint may be reduced by introducing a reactive diluent derived from a vegetable oil and thereby producing a coating partly based on a renewable resource. A reactive diluent acts as a solvent in the liquid paint, lowering the viscosity, and is then incorporated into the film during cure. In the present study, rape seed methyl ester (RME) has been evaluated as reactive diluent in a thermally cured hydroxyl-functional polyester/melamine system. RME has suitable diluting properties and functionality to be incorporated into the dry coating. Dynamic mechanical analysis of free standing films shows that the final film properties are affected by presence of reactive diluent, oven temperature, choice of co-solvent, and flash-off period.
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| 21. |
- Johansson, Mats K. G., et al.
(författare)
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Radiation curing of hyperbranched polyester resins
- 2000
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 75:5, s. 612-618
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Tidskriftsartikel (refereegranskat)abstract
- A research area that has obtained increasing interest during the last decade concerns improvement of macromolecular properties by changes in the macromolecular architecture. One group of these materials is dendritic polymers, which are highly branched structures exhibiting very different properties compared with linear polymers. One potential application for these polymers is as radiation curable thermoset resins. This article describes a study where the use of an aliphatic hyperbranched polyester as a base for new radiation curable thermoset resins. The hyperbranched polyesters have been characterized with respect to cure rate and final mechanical properties compared with conventional resins. It is shown that hyperbranched polyesters can be used as versatile scaffolds for various radiation curable resin structures.
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| 22. |
- Krupicka, A., et al.
(författare)
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Mechanical surface characterization : A promising procedure to screen organic coatings
- 2003
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Ingår i: JCT. - 0361-8773. ; 75:939, s. 19-
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Tidskriftsartikel (refereegranskat)abstract
- Two ductile coating materials were subjected to a combined indentation and scratch test procedure designed to screen a predetermined pattern of many small sample surfaces in a limited time. The screening of 50 surface spots ordered in a matrix pattern on the surface was carried out in 4.5 hr. The test provides reproducible data in terms of indentaion modulus, elastic recovery, scratch penetration depth, and scratch residual depth, and also offers the possibility of detecting critical mechanical transitions such as rupture. The presented procedure produces sufficient data in a limited time scale to fulfill the requirements for a fast method to screen coating compositions.
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| 23. |
- Krupicka, A., et al.
(författare)
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The effect of long-term recovery and storage on the mechanical response of ductile poly(urethane) coatings
- 2003
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Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 48:1, s. 14-27
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Tidskriftsartikel (refereegranskat)abstract
- The scope of this work has been to investigate storage and recovery processes in ductile polymer coatings. The effects of storage have been measured in terms of variations in mechanical response with time. The use of contact tests in combination with sophisticated surface imaging tools offered unique possibilities to monitor deformation recovery over long periods of time. The kinetics of the recovery processes has been monitored. Polyurethane coatings were found to recover in a similar fashion to a viscous liquid. By comparing the time scale of the recovery with transient tests, it was evident that this was not a viscoelastic effect. The effect of exposure to water and humidity on deformation response and recovery was significant for polyurethane coatings. In addition, high amounts of pigmentation had a great effect on recovery processes. Surface-, bulk-, and interfacial-properties were greatly affected by storage time.
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| 24. |
- Larsson, G., et al.
(författare)
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Reducing engine noise with an enclosure using micro perforated plate
- 2006
-
Ingår i: EURONOISE - Eur. Conf. Noise Control: Adv. Solutions Noise Control.
-
Konferensbidrag (refereegranskat)abstract
- Ship- and power plant combustion engines are complex technical systems that have been spared from noise reducing measures. Since these types of technical systems are commonly placed in sound-insulated rooms or at locations where the emitted sound does not affect people, little effort has been made to reduce the level of noise. The optimal way to reduce noise is at the source, where the sound creating forces are the target of the measure. However, the complexity of an engine makes this a very time consuming project. Described in this paper, the sound is reduced at the sound path, with an enclosure. For an engine, this is a very effective and feasible solution, which also is relatively fast to design and applicable to many different models. The purpose of this enclosure is to reduce sound power from the engine top with 10 dB(A). One part of this project was to construct a mathematical model for the design of an enclosure prototype. The model simulates a three layer wall, consisting of a micro perforated plate (MPP), an absorber and a solid plate and gives as results the absorption and the transmission. The result was confirmed with measurements. By then using classical room acoustics, it is possible to predict the insertion loss of an enclosure. To facilitate the usage of the mathematic model, a stand alone (C++) design application was created. A prototype was manufactured which was tested on the W6L34SG engine. It was tested with loudspeakers and under real condition. This paper describes the mathematical model of the project and also gives result between calculated and measured acoustic quantities.
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| 25. |
- Salehi Movahed, Alireza
(författare)
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Effect of Wood Constituents Oxidation of Unsaturated Fatty Acids
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This work presents the mechanisms of free radicals in a model system between fatty acids oxidation process and wood components. The aim is to create a better understanding of new environmentally friendly materials for exterior wood protection. The drying mechanisms of the unsaturated fatty acids with wood model system in the real time were monitored by using RT-IR. This method together with SEC and NMR are enormously powerful spectroscopy techniques to determine the physical and chemical properties of fatty acids-wood during the oxidation process over time. In the first part of this study the focus was in a molecular level on oxidation of methyl linoleate mixed with lignin model compounds (1 and 20 wt%). The effect of lignin structures on unsaturation fatty acids oxidation was determined with 1 wt% lignin model compounds. The interaction, coupling reaction and new structure formations were analyzed through 20 wt% of same lignin compounds mixed with 80 wt% methyl linoleate. The oil oxidation interaction mechanisms were also evaluated by using methyl linoleate, methyl oleate and Linola® on real/natural wood (Norwegian Spruce). In the second part of this work, FT-IR and different NMR methods were used as characterization techniques. The results showed that the oxidative drying process of unsaturated fatty acids was indeed affected by wood constituents. The most hydrophobic part of the wood; lignin, interacted with the oxidation process and some lignin structures inhibited or retarded the reaction. Not only the oil structures were affected but also the lignins were to some extent oxidized as a competing reaction with the oil oxidation. However, a formation of chemicals bonds between the oil and the lignin structures was not observed, i.e. the oils were not immobilized on lignin by covalent bond formation to any significant extent. Further, the focus was on oils in wood using NMR and FTIR demonstrated that highly reactive linoleic acid did react in wood significantly, while it was not immobilized to the same extent. Oleic acid on the other hand reacted more sluggish but the reactive part was immobilized in the wood structure. According to the results, it can be concluded that the structure of the oil is crucial in the overall protective performance of the system. This study indicated that the oxidation pattern of fatty acids behaved differently on wood surface. The wood model compounds minimize the complexity of all elements that exist normally in the natural wood. It can also be concluded that different wood components e.g. end group structures, affect the oil drying process in different ways. The fatty acids pattern will affect not only the structure of the oil dried itself but also the surrounding wood materials.
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| 26. |
- Samuelsson, Johan Patrik, et al.
(författare)
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Thiol-ene coupling reaction of fatty acid monomers
- 2004
-
Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 42:24, s. 6346-6352
-
Tidskriftsartikel (refereegranskat)abstract
- The reactivities and reaction rates of the thiol-ene coupling reaction of 2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto acetate and 2-ethyl-(hydroxymethyl)-1,3-propanediol trimercapto propionate with two common unsaturated fatty acid methyl esters (methyl oleate and methyl linoleate) were evaluated. The reactions were monitored with real-time IR and H-1 NMR, which both showed that the mercapto acetate was more reactive than the mercapto propionate. Both thiols were more prone to add to the monounsaturated methyl oleate than to methyl linoleate, which contained two unconjugated double bonds. According to bond energy calculations, the thiol hydrogen of mercapto acetate was somewhat more difficult to abstract than the hydrogen of mercapto propionate. Consequently, the formed S-C bond in the acetate case was stronger than in the propionate case, and so the equilibrium was more shifted toward the addition products. The real-time IR measurements also showed that the cis unsaturation in methyl oleate isomerized much more quickly than that in methyl linoleate, and this also had an impact on the overall addition rate of the thiols because a trans unsaturation was more reactive than a cis unsaturation. The higher isomerization rates in the oleate systems, compared with those of the linoleate systems, was suggested to be due to a more restricted rotation along the C-C bond of the reacted unsaturation in linoleate. This study showed the importance of trans unsaturations in obtaining reasonable reaction rates in thiol-ene reactions with fatty acid derivatives.
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| 27. |
- Simpson, Neil, et al.
(författare)
-
Thiol-functionalized poly(omega-pentadecalactone) telechelics for semicrystalline polymer networks
- 2008
-
Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 41:10, s. 3613-3619
-
Tidskriftsartikel (refereegranskat)abstract
- Semicrystalline macromonomers based on poly(pentadecalactone), PPDL, have been synthesized by the lipase-catalyzed ring-opening of the otherwise chemically inert pentadecalactone monomer. The macromonomers were designed to have reactive thiols as end groups by the appropriate choice of initiator and chain terminator. The thiol functional macromonomers were then used together with ene monomers to give crosslinked thin films after irradiation in the molten state by UV light in the presence of a photoinitiator (Irgacure 65 1). Two different ene monomers were used, i.e., a tetrafunctional norbornene species and a trifunctional allyl ether maleate species, and resulted in semicrystalline cured films when cured with PPDL. An amorphous, commercially available, trifunctional thiol, trimethylolpropane tri(3-mercaptopropionate), TRIS, was also used for network formation in order to better understand the effect of crystallinity. All thiol-ene systems were found to be readily photopolymerised to high conversion. The PPDL-based networks were semicrystalline in the crosslinked state where the degree of crystallinity was found to depend on the nature of the cross-linker. Networks based on TRIS were found to be amorphous.
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| 28. |
- Xing, K. Z., et al.
(författare)
-
The electronic and geometric structures of neutral and potassium-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy
- 1996
-
Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 76:1-3, s. 263-267
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic and geometric structures of poly [3-(4-octylphenyl)thiophene] have been studied by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS, respectively). Thermochromic effects, and new charge induced states generated by potassium doping, have been observed by direct UPS measurements. The experimental results are in very good agreement with the results of theoretical quantum chemical calculations performed with the Austin Model 1 semi-empirical model and the valence-effective Hamiltonian pseudo-potential model.
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| 29. |
- Xing, K. Z., et al.
(författare)
-
The electronic structure of neutral and alkali metal-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy
- 1996
-
Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 80:1, s. 59-66
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of poly [3-(4-octylphenyl)thiophene] (POPT) has been studied by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS), as well as by quantum chemical calculations. Both temperature-dependent effects on the electronic structure of the neutral system, as well as the generation of new electronic states induced by doping with alkaline metals, have been observed. The experimental results are in good agreement with the results of the quantum chemical calculations.
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| 30. |
- Yi, Chuixiang, et al.
(författare)
-
Climate control of terrestrial carbon exchange across biomes and continents
- 2010
-
Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 5:3
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.
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| 31. |
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| 32. |
- Ansari, Farhan, et al.
(författare)
-
Interface tailoring through covalent hydroxyl-epoxy bonds improves hygromechanical stability in nanocellulose materials
- 2016
-
Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 134, s. 175-183
-
Tidskriftsartikel (refereegranskat)abstract
- Wide-spread use of cellulose nanofibril (CNF) biocomposites and nanomaterials is limited by CNF moisture sensitivity due to surface hydration. We report on a versatile and scalable interface tailoring route for CNF to address this, based on technically important epoxide chemistry. Bulk impregnation of epoxide-amine containing liquids is used to show that CNF hydroxyls can react with epoxides at high rates and high degree of conversion to form covalent bonds. Reactions take place inside nanostructured CNF networks under benign conditions, and are verified by solid state NMR. Epoxide modified CNF nanopaper shows significantly improved mechanical properties under moist and wet conditions. High resolution microscopy is used in fractography studies to relate the property differences to structural change. The cellulose-epoxide interface tailoring concept is versatile in that the functionality of molecules with epoxide end-groups can be varied over a wide range. Furthermore, epoxide reactions with nanocellulose can be readily implemented for processing of moisture-stable, tailored interface biocomposites in the form of coatings, adhesives and molded composites.
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| 33. |
- Bagni, T., et al.
(författare)
-
Modeling Results of the Quench Behavior of a Nb-Ti Canted-Cosine-Theta Corrector Magnet for LHC
- 2024
-
Ingår i: IEEE transactions on applied superconductivity (Print). - : IEEE. - 1051-8223 .- 1558-2515. ; 34:5
-
Tidskriftsartikel (refereegranskat)abstract
- A newly designed superconducting magnet of the Canted-Cosine-Theta (CCT) type was developed as a result of a collaboration between Swedish universities (Uppsala and Linneaus) and Swedish industries. This magnet was designed to function as a replacement of the present LHC orbit corrector magnets, which are approaching their end of life due to the radiation load. As a result, the new CCT magnet was developed to be more radiation tolerant and to constitute a one-to-one replacement to the currently installed version, which is a 1 m long 70 mm double aperture dipole magnet. The final magnet, which is currently under construction, will be tested at FREIA laboratory at Uppsala University and generate a magnetic field of 3.3 T and an integrated field of 2.8 Tm at about 85 A. To examine the magnet quench behavior and to identify a suitable quench protection system, the 3D electro-magnetic and thermal behavior of the coil was modeled using the RAT-Raccoon software. Based on the simulation results, a Metrosil varistor was selected to protect the magnet during the test. In this article, we report the results of the numerical analysis. The magnet model is equipped with a spot heater to initialize the quench and the temperature and voltages are monitored during the avalanche effect. The simulated current decay and the hot-spot temperature are analyzed with a focus on the impact of quench-back on the magnet protection.
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| 34. |
- Bexell, U., et al.
(författare)
-
A ToF-SIMS study of linseed oil bonded to mercapto silane treated aluminium
- 2004
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 231-2, s. 362-365
-
Tidskriftsartikel (refereegranskat)abstract
- ToF-SIMS has been used to analyse an aluminium surface treated with a vegetable oil using a mercapto silane as a coupling agent between the aluminium substrate and the vegetable oil. The coupling between the vegetable oil and the mercapto silane was obtained through a photoinduced thiol-ene reaction using UV-radiation. The ToF-SIMS results show that the desired thiolene reaction has taken place between the unsaturated parts of the vegetable oil and the thiol groups of the mercapto silane via the thiol-ene reaction forming a surface film.
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| 35. |
- Bexell, U., et al.
(författare)
-
A tribological study of a novel pre-treatment with linseed oil bonded to mercaptosilane treated aluminium
- 2003
-
Ingår i: Surface & Coatings Technology. - 0257-8972 .- 1879-3347. ; 166:03-feb, s. 141-152
-
Tidskriftsartikel (refereegranskat)abstract
- In sheet metal forming processes, lubricants are necessary in order to prevent galling, i.e. material transfer from the sheet metal to the tool surface and to control friction. Today, dry lubricants are increasingly being used for solving this problem. Among these, multifunctional coatings, often referred to as permanent coatings, normally based on organic resins, are lubricants which have the potential to increase the formability without additional lubrication, give corrosion protection, fingerprint and scratch resistance during handling and transport and finally, serve as a pre-treatment before painting. With increasing concern about the environment and human health it is important to develop new environmentally friendly pre-treatments in the surface engineering of metal substrates. This is mainly due to the toxic and carcinogenic properties of the chromium based surface pre-treatments frequently used in the industry. During the last decade, simple solution-dip silane based pre-treatments have emerged as promising candidates for the replacement of currently used pre-treatments of metals. A silane film can give good corrosion protection properties but is often too thin to prevent galling under a forming operation. A renewed interest for using vegetable oils in surface engineering has appeared lately due to several factors. Vegetable oils are renewable resources, modem technology can produce more well defined and pure oils, and the fatty acid content can be altered with modern crops development techniques. With the proper choice of silane pre-treatment of a metal surface, a vegetable oil can be coupled to the surface and give the desired lubrication properties. In this paper, aluminium sheets have been pre-treated with a mercapto silane after which a vegetable oil has been attached. The coupling between the silane and the oil was obtained through a photoinduced thiol-ene reaction using UV-radiation. The influence of different process parameters on the friction and wear behaviour was evaluated using modified scratch testing. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and contact angle measurements were used to characterise the as-deposited surface films and their tribological behaviour, i.e. failure mechanisms. The results obtained show that the unsaturated vegetable oil has reacted with the thiol groups via the thiol-ene reaction forming a surface film. Also, the results show that the thickness of the films is of importance for the tribological characteristics, i.e. a too thin layer (less than 25 A in the present work) results in high friction and severe adhesive wear. However, a thicker layer with enhanced load carrying capacity can be produced with a proper heat treatment of the deposited vegetable oil. Finally, the results show that thick (more than 200 Angstrom in the present work) silane films are sensitive to brittle fracture when exposed to a sliding contact.
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| 36. |
- Bexell, Ulf, et al.
(författare)
-
Bonding of vegetable oils to mercapto silane treated metal surfaces : Surface engineering on the nano scale
- 2006
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 838-841
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper the bonding of thin vegetable oil films on mercapto silane treated aluminium surfaces has been studied. The silane molecules are attached to the surface by metal-oxygen-silicon bonds. The coupling between the unsaturated bonds of the vegetable oil and the thiol functionalised surface was obtained through a photoinduced thiol-ene reaction. The surfaces were characterised by X-ray photoelectron spectroscopy (XPS). Vegetable oil contains both saturated and unsaturated carbon chains. For the reactions investigated in this study it is the unsaturated carbon chains that can react by a thiol-ene reaction and the results indicate that it is possible to attach a vegetable oil to a metal surface pre-treated with a thiol functionalised silane.
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| 37. |
- Blomfeldt, Thomas, 1982-
(författare)
-
Gluten Protein-Based Microcellular Foams and Composites: Development and Functional Properties
- 2010
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Most common foams are produced from non-renewable resources (e.g., synthetic plastics),with a number of environmental concerns, hence there is a demand for alternative bio-derivedfoam materials. Wheat gluten protein is widely known to have excellent foaming properties(e.g., in bread making) and is a possible alternative resource for making foam products.Gluten foams were produced using a lyophilization process (freeze-drying) and variousgluten/water-based mixtures were studied. Foams with varying properties were obtained bymixing various amounts of wheat gluten with glycerol (plasticizer) and bacterial cellulosefibers (reinforcement). The gluten foams looked like bread with a beige color and few visuallydetectable surface pores. They were generally characterized as having an open cell structurewith a porosity in the range 75-85% and pore sizes ranging between 20 and 73 μm. Differentmechanical properties were obtained by using varying gluten concentrations and the differentadditives. Plasticizing with glycerol lead to increased flexibility of the foams, with the abilityto recover up to 95% after being compressed by 80%. By reinforcing with bacterial cellulosefibers the material became stiffer, with an increased elastic modulus. Confocal lasermicroscopy revealed that the fibers and gluten interacted. Analyzing the protein structure ofthe foams revealed that the different additives resulted in structures with different proteinpatterns. The samples containing glycerol were more polymerized and less extractable in SDS,whereas the fiber containing samples were only polymerized in small regions and easilyextracted in SDS. Generally the gluten foams had low conductivity values, with some valuesbelow 0.05 W/(m K), which was found to be dependant on density and pore structure. Glutenfoams were also shown to be more difficult to ignite when compared to other conventionalfoams. It was further observed that the foams did not drip making it increasingly difficult forthe fire to spread.
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| 38. |
- Bäckström, Torbjörn, et al.
(författare)
-
Paradoxical effects of GABA-A modulators may explain sex steroid induced negative mood symptoms in some persons
- 2011
-
Ingår i: Neuroscience. - Oxford : Elsevier BV. - 0306-4522 .- 1873-7544. ; 191:Special issue, s. 46-54
-
Forskningsöversikt (refereegranskat)abstract
- Some women have negative mood symptoms, caused by progestagens in hormonal contraceptives or sequential hormone therapy or by progesterone in the luteal phase of the menstrual cycle, which may be attributed to metabolites acting on the GABA-A receptor. The GABA system is the major inhibitory system in the adult CNS and most positive modulators of the GABA-A receptor (benzodiazepines, barbiturates, alcohol, GABA steroids), induce inhibitory (e.g. anesthetic, sedative, anticonvulsant, anxiolytic) effects. However, some individuals have adverse effects (seizures, increased pain, anxiety, irritability, aggression) upon exposure. Positive GABA-A receptor modulators induce strong paradoxical effects including negative mood in 3%-8% of those exposed, while up to 25% have moderate symptoms. The effect is biphasic: low concentrations induce an adverse anxiogenic effect while higher concentrations decrease this effect and show inhibitory, calming properties. The prevalence of premenstrual dysphoric disorder (PMDD) is also 3%-8% among women in fertile ages, and up to 25% have more moderate symptoms of premenstrual syndrome (PMS). Patients with PMDD have severe luteal phase-related symptoms and show changes in GABA-A receptor sensitivity and GABA concentrations. Findings suggest that negative mood symptoms in women with PMDD are caused by the paradoxical effect of allopregnanolone mediated via the GABA-A receptor, which may be explained by one or more of three hypotheses regarding the paradoxical effect of GABA steroids on behavior: (1) under certain conditions, such as puberty, the relative fraction of certain GABA-A receptor subtypes may be altered, and at those subtypes the GABA steroids may act as negative modulators in contrast to their usual role as positive modulators; (2) in certain brain areas of vulnerable women the transmembrane C1(-) gradient may be altered by factors such as estrogens that favor excitability; (3) inhibition of inhibitory neurons may promote disinhibition, and hence excitability. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain. (C) 2011 Published by Elsevier Ltd on behalf of IBRO.
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| 39. |
- Claesson, Hans, et al.
(författare)
-
Rheological behaviour during UV-curing of a star-branched polyester
- 2002
-
Ingår i: Progress in organic coatings. - 0300-9440 .- 1873-331X. ; 44:1, s. 63-67
-
Tidskriftsartikel (refereegranskat)abstract
- Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.
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| 40. |
- Claesson, Hans, et al.
(författare)
-
Semi-crystalline thermoset resins : tailoring rheological properties in melt using comb structures with crystalline grafts
- 2004
-
Ingår i: Progress in organic coatings. - : Elsevier BV. - 0300-9440 .- 1873-331X. ; 49:1, s. 13-22
-
Tidskriftsartikel (refereegranskat)abstract
- Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.
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| 41. |
- Claesson, Hans, et al.
(författare)
-
Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity
- 2002
-
Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 43:12, s. 3511-3518
-
Tidskriftsartikel (refereegranskat)abstract
- A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.
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| 42. |
- Glauser, T., et al.
(författare)
-
A comparison of radiation and thermal curing of thick composites
- 2000
-
Ingår i: Macromolecular materials and engineering. - 1438-7492 .- 1439-2054. ; 274:1, s. 25-30
-
Tidskriftsartikel (refereegranskat)abstract
- This work aimed to compare three different techniques to cure thick composite matrices to see the effect of the process on the network and the thermomechanical properties of the polymer matrix. Two different thermoset resins. one acrylate and one methacrylate, have been free-radically cured with high-energy electron beam (EB), ultra-violet light (UV) ol heat (thermal). The differences in curing mechanisms as well as the thermomechanical properties of the cured resins have been investigated. For this type of resins, EB-cured samples showed the highest thermo-mechanical properties and the lowest residual unsaturation. Thermally cured resins showed similar properties, but with drawbacks such as long curing cycles and thermal degradation in the matrix. The cure did not proceed to the same extent in the UV-cured samples. But the simplicity of the curing equipment makes UV-curing an interesting complement to thermal or EB-curing.
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| 43. |
- Glauser, T., et al.
(författare)
-
Electron-beam curing of thick thermoset composites : Effect of temperature and fiber
- 2000
-
Ingår i: Macromolecular materials and engineering. - 1438-7492 .- 1439-2054. ; 274:1, s. 20-24
-
Tidskriftsartikel (refereegranskat)abstract
- Electron-beam curing of thermoset resins used in fiber-reinforced composites has been investigated. Two resins, a bisphenol-A acrylate and methacrylate, were used as model systems. The temperature was monitored during cure to know the thermal history of the composite during cure. The thermo-mechanical properties were measured on the cured samples. It could be seen that all these values were influenced by the nature (glass or carbon) and amount (0-50 wt.-%) of fiber. A linear correlation was found between the maximum temperature during cure and the glass transition temperature. It was shown that it is possible to compensate for alack of heat during dire in systems with too low exotherms. Some influence on the network homogeneity was also noticed when the thermal energy available during cure was too low.
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| 44. |
- Glauser, T., et al.
(författare)
-
Toughening of electron-beam cured acrylate resins
- 2000
-
Ingår i: Macromolecular materials and engineering. - 1438-7492 .- 1439-2054. ; 280:08-jul, s. 20-25
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to improve the toughness of EB-cured acrylate thermost resins by using hyperbranched aliphatic polyesters as additives to obtain a liquid-liquid phase-separated resin. The hyperbranched polyester can be considered as a hydroxyl functional scaffold, on which functional groups were reacted by control phase separation and crosslinking. Alkyl chains of different lengths attached to the scaffold controlled phase separation. The amount of crosslinking within the rubbery particle and between the particles and the matrix was set by the percentage of methacrylate groups. A good phase separation was obtained; therefore, T-g decreased only slightly compared to the pure acrylate. The K-IC value of the cured resins was increased by 30%. The phase-separated resins showed stability with time and no significant increase in particle size was noticed after 18 months.
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| 45. |
- Haraldsson, Klas Tommy, 1968-
(författare)
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Fabrication of polymeric microfluidic devices via photocurable liquid monomers
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Microfluidic devices have long been considered an ideal tool for rapid and inexpensive chemical analysis and reactions in areas ranging from point-of-care health to national security applications. However, fabricating microfluidic devices is time consuming, difficult and above all expensive. In commercial applications many thousand units need to be sold before the development costs are recovered. The problem is compounded since most microfluidic devices do not have generalized architectures which means that each end use requires a specialized design. The microfluidics marketplace can therefore be seen as being composed of 1000’s of niche markets. To address development costs, there is clearly a need for a versatile technology that can be used for many different applications and that enables rapid testing and optimization of new designs. This work describes such a technology: Contact Liquid Photolithographic Polymerization (CLiPP). The thesis consists of two parts: polymerization kinetics and the fabrication of polymeric microfluidic devices via CLiPP. The photopolymerization kinetics is evaluated for a number of monomer types, and the results are used to assess their suitability in the CLiPP process. Vinyl ether/maleate photoinitiated copolymerization is examined in detail. It is shown that the polymerization kinetics is dramatically influenced by the availability of easily abstractable hydrogens The presence of α-hydrogens adjacent to the vinyl ether functional group reduces the polymerization rate and the dependence of the polymerization rate as a function of initiation rate. Also, photoinitiated acrylate and methacrylate polymerization kinetics are presented. The kinetics results in these three monomer types are used to explain the different patterning properties of the monomer functionalities used in the CLiPP process, in which acrylates show enhanced patterning properties compared to methacrylates. The polymerization kinetics is studied with traditional tools and methods: photo Differential Scanning Calorimetry (photo-DSC), photo Fourier Transform Real Time Infrared Spectroscopy (photo-RTIR), and photo Real Time Electron Paramagnetic Spectroscopy (ESR). The microfluidic fabrication is performed via both in-house fabricated and commercially available CLiPP-specific hardware. The patterning qualities of the structures are evaluated via Scanning Electron Microscopy (SEM) and Optical Microscopy. The finished devices are used in their intended environment and evaluated in suitable manners to assess their utility. In this thesis, the development and design of specialized CLiPP fabrication machines, fabrication techniques and resulting microfluidic device features are presented anddiscussed. It is shown that the CLiPP scheme enables features such as 3 dimensional (3D) capabilities for minimized device footprints, a very large number of polymeric materials for optimized device components as well as facile integration of prefabricated components. Also, covalent layer adhesion and permanent surface modifications via living radical processes are demonstrated. These capabilities are exemplified in a number of examples that range from a 3D fluidic channel maze with separated fluidic streams and a device with independently moveable parts to a device constructed from multiple polymeric materials and devices with permanently modified surfaces, Also, batch processing capabilities are shown through fabrication of 400 identical undercut microstructures. Rapid and inexpensive design evaluations, multiple materials capabilities and the ability to seamlessly incorporate prefabricated microstructures of the CLiPP process strongly encourages continued method development. The future work that remains to be addressed is divided into two parts. First, to enable novel research devices, new polymer materials with enhanced mechanical and surface properties must be developed. Also, integration of prefabricated microstructures such as sensors and actuators has to be incorporated in a reproducible and rational manner. Secondly, to enable device mass fabrication, new automated equipment is to be developed in order to utilize the full batch processing potential of CLiPP.
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| 46. |
- Haraldsson, Klas Tommy, et al.
(författare)
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The Effects of Abstractable Hydrogen in Radical Photopolymerization of Maleate/Vinyl Ether Monomers Studied with EPR and Photo-RTIR
- 2010
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Ingår i: Journal of Polymer Science Part A. - : Wiley. - 0887-624X .- 1099-0518. ; 48:13, s. 2810-2816
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Tidskriftsartikel (refereegranskat)abstract
- In this contribution, the influence of abstractable hydrogen on the kinetics of photopolymerized vinyl ether/maleate monomer formulations is reported. The effects of chain transfer on the polymerization rate were studied with photo real-time Infra Red (IR) for formulations composed of equimolar amounts of diethyl (DEMA) and three different vinyl ethers; methyl hexyl vinyl ether where the abstractable hydrogens adjacent to the vinyl functionality have been replaced with methyl groups, ethyl hexyl vinyl ether (EHVE) which has two easily abstractable alpha-hydrogens and triethylene glycol methyl vinyl ether (TEGMVE), which has several abstractable hydrogens. Four conclusions are drawn from these studies: (i) the vinyl ether/maleate kinetics differs significantly from the classical expression R-p = KI0.5, with recorded exponential factors of 0.84 +/- 0.04 in the absence of easily abstractable hydrogens; (ii) the presence of abstractable hydrogens significantly changes the kinetics of vinyl ether/maleate polymerizations with recorded exponential factors of 0.55 +/- 0.04 for EHVE/DEMA and 0.70 +/- 0.04 for TEGMVE/DEMA; (iii) the presence of easily abstractable hydrogens leads to a preferential consumption of maleates; and (iv) electron paramagnetic resonance studies show that vinyloxy-like radicals constitute the majority of the radicals in the systems with easily abstractable hydrogens.
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| 47. |
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| 48. |
- Hedenqvist, Mikael S., et al.
(författare)
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Transport properties of hyperbranched and dendrimer-like star polymers
- 2000
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Ingår i: Polymer. - 0032-3861 .- 1873-2291. ; 41:5, s. 1827-1840
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Tidskriftsartikel (refereegranskat)abstract
- Moisture transport properties were assessed by sorption and desorption measurements on hydroxyl-functional hyperbranched polyesters based on 2,2-bis(methylol) propionic acid (bis-MPA) as AB(2)-monomer with ethoxylated pentaerythritol. A series of these polymers with different molar masses were studied. For the first time, it is reported that sigmoidal sorption curves were successfully modelled using a time-dependent surface boundary concentration, where the relaxation time was obtained from the mechanical stress relaxation data. The zero concentration diffusivities were very small and comparable with the values of fully amorphous poly(vinyl alcohol). Both the diffusivity data and the stress relaxation data indicated that these materials were plasticized by moisture. Ethylene glycol transport properties were measured on a hexadecanoate(C16)-terminated bis-MPA hyperbranched polymer. The replacement of the hydroxyl groups with C16 paraffin tails resulted in an increase in solute diffusivity despite the fact that these polymers became semicrystalline. The shape of the desorption curves indicated that continuous micropores were present and facilitated mass transport. The moisture transport properties were also measured on a series of semicrystalline dendrimer-like star poly(epsilon-caprolactone(s)). The low measured densities of these highly crystalline dendrimers confirmed that the porosity, as indicated by the shape of the desorption curves, had to be discontinuous. The porosity in the (C16)-terminated and the poly(epsilon-caprolactone(s)) was impossible to eliminate by applying a high external pressure during crystallization. A collective view of all the results obtained confirm that the transport properties are primarily controlled by the hydroxyl group concentration.
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| 49. |
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| 50. |
- Henriksson, Marielle, et al.
(författare)
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Novel nanocomposite concept based on cross-linking of hyperbranched polymers in reactive cellulose nanopaper templates
- 2011
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Ingår i: Composites Science And Technology. - : Elsevier BV. - 0266-3538 .- 1879-1050. ; 71:1, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- Cellulosic fibers offer interesting possibilities for good interfacial adhesion due to the high density of hydroxyl groups at the surface. in the present study, the potential of a new nanocomposite concept is investigated, where a porous cellulose nanofiber network is impregnated with a solution of reactive hyperbranched polyester. The polymer is chemically cross-linked to form a solid matrix. The resulting nanocomposite structure is unique. The matrix surrounds a tough nanopaper structure consisting of approximately 20 nm diameter nanofibers with an average interfiber distance of only about 6 nm. The cross-linked polymer matrix shows strongly altered characteristics when it is cross-linked in the confined space within the nanofiber network, including dramatically increased T-g, and this must be due to covalent matrix-nanofiber linkages.
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