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Sökning: LAR1:lu > Mittuniversitetet > Tidskriftsartikel

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1.
  • Albani, Giorgia, et al. (författare)
  • Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
  • 2016
  • Ingår i: Measurement Science and Technology. - IOP Publishing. - 0957-0233. ; 27:11
  • Tidskriftsartikel (refereegranskat)abstract
    • The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
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2.
  • Alem, Yonas, et al. (författare)
  • The persistence of subjective poverty in urban Ethiopia
  • 2014
  • Ingår i: World Development. - 0305-750X .- 1873-5991. ; 56:1, s. 51-61
  • Tidskriftsartikel (refereegranskat)abstract
    • Using data spanning 15 years, we study subjective and consumption poverty in urban Ethiopia. Despite rapid economic growth and declining consumption poverty, subjective poverty remains largely unchanged. We find that households with a history of poverty continue to perceive themselves as poor even if their material consumption improves. The relative economic position of households is a strong determinant of subjective poverty. Having some type of employment makes households less likely to perceive themselves as poor, even if they remain in objective poverty. We argue that any analysis to measure the impact of growth on welfare should also encompass subjective measures.
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3.
  • Alves, Luis, et al. (författare)
  • Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents
  • 2016
  • Ingår i: Cellulose. - Springer. - 0969-0239. ; 23:1, s. 247-258
  • Tidskriftsartikel (refereegranskat)abstract
    • The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.
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4.
  • Alves, Luis, et al. (författare)
  • Dissolution state of cellulose in aqueous systems. 2. Acidic solvents
  • 2016
  • Ingår i: Carbohydrate Polymers. - Elsevier. - 0144-8617. ; 151, s. 707-715
  • Tidskriftsartikel (refereegranskat)abstract
    • Cellulose is insoluble in water but can be dissolved in strong acidic or alkaline conditions. How well dissolved cellulose is in solution and how it organizes are key questions often neglected in literature. The typical low pH required for dissolving cellulose in acidic solvents limits the use of typical characterization techniques. In this respect, Polarization Transfer Solid State NMR (PT ssNMR) emerges as a reliable alternative. In this work, combining PT ssNMR, microscopic techniques and X-ray diffraction, a set of different acidic systems (phosphoric acid/water, sulfuric acid/glycerol and zinc chloride/water) is investigated. The studied solvent systems are capable to efficiently dissolve cellulose, although degradation occurs to some extent. PT ssNMR is capable to identify the liquid and solid fractions of cellulose, the degradation products and it is also sensitive to gelation. The materials regenerated from the acidic dopes were found to be highly sensitive to the solvent system and to the presence of amphiphilic additives in solution.
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5.
  • Alves, L., et al. (författare)
  • Unusual extraction and characterization of nanocrystalline cellulose from cellulose derivatives
  • 2015
  • Ingår i: Journal of Molecular Liquids. - Elsevier. - 0167-7322. ; 210, s. 106-112
  • Tidskriftsartikel (refereegranskat)abstract
    • Unlike many nanomaterials, nanocrystalline cellulose (CNC) is not synthesized from molecular or atomic components but rather extracted from naturally occurring cellulose. Undoubtedly, the exploitation of CNCs will become a bridge between nanoscience and natural resource products, which could play a major role in reviving the forest industry. In this work, CNC was successfully extracted from unusual sources, hydroxypropyl methylcellulose (HPMC) and carboxymethylcellulose (CMC). The extracted crystallites were purified and further characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and dynamic light scattering (DLS). The average size of the CNCs extracted from HPMC and CMC was found to be less (and with lower zeta potential) than the ones extracted from microcrystalline cellulose (MCC). On the other hand, FTIR and XRD revealed that native HPMC and CMC are unexpectedly highly crystalline and hence can be used as a source for CNCs. (C) 2014 Elsevier B.V. All rights reserved.
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6.
  • Amenitsch, Hans, et al. (författare)
  • Bile salts form lyotropic liquid crystals
  • 2003
  • Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - Elsevier. - 0927-7757. ; 213:1, s. 79-92
  • Tidskriftsartikel (refereegranskat)abstract
    • A reinvestigation of the phase diagrams relative to some conjugated and non-conjugated bile salts in water has demonstrated the formation of lyotropic liquid crystalline phases, in contradiction with generally accepted statements. The phase behaviour is complex and the phase diagrams are unusual, compared to most surfactants and lipids. In particular, coexistence of liquid crystalline phases with crystals has been obser ed. The formation of liquid crystalline phases requires very long equilibration times and the thermal stability of the lyotropic phases is moderate. The observed structure is tentatively assumed to be of the reverse hexagonal type. Structural relations with currently accepted models for the organisation of bile salts into micelles and solid form have been found. (C) 2002 Elsevier Science B.V. All rights reserved.
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7.
  • Anastasopoulos, Michail, et al. (författare)
  • Multi-Grid detector for neutron spectroscopy : : Results obtained on time-of-flight spectrometer CNCS
  • 2017
  • Ingår i: Journal of Instrumentation. - IOP Publishing. - 1748-0221. ; 12:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The Multi-Grid detector technology has evolved from the proof-of-principle and characterisation stages. Here we report on the performance of the Multi-Grid detector, the MG.CNCS prototype, which has been installed and tested at the Cold Neutron Chopper Spectrometer, CNCS at SNS. This has allowed a side-by-side comparison to the performance of 3He detectors on an operational instrument. The demonstrator has an active area of 0.2 m2. It is specifically tailored to the specifications of CNCS. The detector was installed in June 2016 and has operated since then, collecting neutron scattering data in parallel to the He-3 detectors of CNCS. In this paper, we present a comprehensive analysis of this data, in particular on instrument energy resolution, rate capability, background and relative efficiency. Stability, gamma-ray and fast neutron sensitivity have also been investigated. The effect of scattering in the detector components has been measured and provides input to comparison for Monte Carlo simulations. All data is presented in comparison to that measured by the 3He detectors simultaneously, showing that all features recorded by one detector are also recorded by the other. The energy resolution matches closely. We find that the Multi-Grid is able to match the data collected by 3He, and see an indication of a considerable advantage in the count rate capability. Based on these results, we are confident that the Multi-Grid detector will be capable of producing high quality scientific data on chopper spectrometers utilising the unprecedented neutron flux of the ESS.
8.
  • Anderbrant, Olle, et al. (författare)
  • Field Response of Male Pine Sawflies, Neodiprion sertifer (Diprionidae), to Sex Pheromone Analogs in Japan and Sweden.
  • 2010
  • Ingår i: Journal of Chemical Ecology. - Springer. - 1573-1561. ; 36, s. 969-977
  • Tidskriftsartikel (refereegranskat)abstract
    • The pine sawfly Neodiprion sertifer (Geoffroy) uses the acetate or propionate of (2S,3S,7S)-3,7-dimethyl-2-pentadecanol (diprionol) as pheromone components, with the (2S,3R,7R)-isomer being antagonistic, synergistic, or inactive according to the population tested. In this study, we tested the attraction of males to the acetates of three analogs of diprionol, each missing one methyl group, viz. (2S,7S)-7-methyl-2-pentadecanol, (2S,6S)-2,6-dimethyl-1-tetradecanol, and (2S,3S)-3-methyl-2-pentadecanol. None of the analogs alone, or in combination with diprionol acetate, was attractive in Sweden, even at 100 times the amount of diprionol acetate attractive to N. sertifer. In Japan, the acetate of (2S,3S)-3-methyl-2-pentadecanol attracted males when tested in amounts 10-20 times higher than the acetate pheromone component. The acetate esters of the (2S,3R)-analog and the (2S,3R,7R)-isomer of diprionol also were tested in combination with the pheromone compound (acetate ester). Both compounds caused an almost total trap-catch reduction in Sweden, whereas in Japan they appear to have relatively little effect on trap capture when added to diprionol acetate. Butyrate and iso-butyrate esters of diprionol were unattractive to N. sertifer in Sweden. In summary, there exists geographic variation in N. sertifer in responses to both diprionyl acetate and some of its analogs.
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9.
10.
  • Anderbrant, Olle, et al. (författare)
  • Release of sex pheromone and its precursors in the pine sawfly Diprion pini (Hym., Diprionidae)
  • 2005
  • Ingår i: Chemoecology. - Birkhaüser. - 1423-0445. ; 15:3, s. 147-151
  • Tidskriftsartikel (refereegranskat)abstract
    • The first identification of a sex pheromone of a pine sawfly (Hymenoptera, Diprionidae) dates back almost thirty years. Since then, female-produced pheromones of over twenty diprionid species have been investigated by solvent extraction followed by separation and identification. However, no study has shown what the females actually release. Collection of airborne compounds using absorbtion on charcoal filter as well as solid phase microextraction (SPME) followed by analysis employing gas chromatography combined with mass spectrometry (GC-MS), revealed an unusual system in Diprion pini, in which the pheromone precursor alcohol, 3,7-dimethyl-2-tridecanol, is released together with acetic, propionic, butyric and isobutyric acids. The corresponding acetate, propionate and butyrate esters of 3,7-dimethyl-2-tridecanol were also found in the samples. All esters were electrophysiologically active, and the propionate and isobutyrate were attractive in trapping experiments. Based on these and earlier reported results, it seems that at least in part of its range, the pheromone response of D. pini is not very specific with regard to the functional group, as long as this is an ester.
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