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Sökning: LAR1:lu > Mittuniversitetet > Tidskriftsartikel

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  • 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.
  • Alves, L., et al. (författare)
  • Unusual extraction and characterization of nanocrystalline cellulose from cellulose derivatives
  • 2015
  • Ingår i: Journal of Molecular Liquids. - 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. © 2014 Elsevier B.V.All rights reserved.
  • Amenitsch, H, 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<br /> 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.
  • 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.
  • Anderbrant, Olle, et al. (författare)
  • Geographic variation in the field response of male European pine sawflies, Neodiprion sertifer , to different pheromone stereoisomers and esters
  • 2000
  • Ingår i: Entomologia Experimentalis et Applicata. - Blackwell Publishing. - 0013-8703. ; 95:3, s. 229-239
  • Tidskriftsartikel (refereegranskat)abstract
    • The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera: Diprionidae), is a widespread and economically important forest insect. The sex pheromone communication system of this species has been previously investigated in North America, Japan and Europe, with the acetate or propionate of the alcohol (2S,3S,7S)-3,7-dimethyl-2-pentadecanol (diprionol) shown to be the main pheromone component. In some locations, male attraction either increased or decreased by the addition of the (2S,3R,7R)-diprionyl acetate isomer. However, these studies were made with different batches of synthetic pheromones, with different types of traps and according to different procedures, so the observed differences might not reflect true geographic variation. Here we investigate the geographic pattern of male sawfly response by using identical chemicals, traps and experimental procedures at eight field sites ranging from Japan in the east to Canada in the west. We found an increased inhibitory effect of the (2S,3R,7R)-isomer from Japan and Siberia to Europe. At the eastern sites, increasing amounts of the (2S,3R,7R)-isomer up to and equal to the amount of the (2S,3S,7S )-isomer, did not influence the trap catch, whereas at sites in Europe, as little as 1% of the (2S,3R,7R)-isomer almost completely inhibited the attraction. The response of the North American population was intermediate. The only site in which the (2S,3R,7R)-isomer was essential for the attraction of males was in Siberia. A similar pattern was found for the (2S,3R,7S)-isomer. Both the acetate and the propionate form of the (2S,3S,7S)-isomer were attractive by themselves in Japan, Europe and North America, and neither the (2S,3R,7S)-isomer nor the (2S,3R,7R)-isomer alone were attractive, in the acetate or propionate form. We discuss the significance of our findings for the development of more efficient monitoring schemes and for the causes of population divergence and speciation in the European pine sawfly.
  • Anderbrant, Olle, et al. (författare)
  • Pheromone mating disruption of the pine sawfly Neodiprion sertifer : : is the size of the treated area important?
  • 2002
  • Ingår i: Iobc/Wprs Bulletin. - Monfavet. - 1027-3115. ; 25:9, s. 111-116
  • Tidskriftsartikel (övrigt vetenskapligt)abstract
    • Few attempts to control forest insects by means of pheromone mating disruption have<br /> been reported. The first such experiments with the European pine sawfly, Neodiprion sertifer<br /> (Hymenoptera: Diprionidae), resulted in nearly complete trap catch reduction, but no effects on<br /> population density or sex ratio were noted. Unmated females lay eggs, which develop into males<br /> only. Therefore, if mating disruption would be successful, a more male-biased sex ratio is<br /> expected the next generation. One possible explanation for the early results is that mated females<br /> disperse into the treated area, and thus obscure the effects of the treatment. In order to reduce the<br /> effect of such immigrating females, the treated area was increased in the experiment described<br /> here from the earlier used 0.5 – 4 ha to 25 ha. The acetate of erythro-3,7-dimethyl-2-<br /> pentadecanol was used for disruption and released from dispensers every 10 m. The influence on<br /> male orientation was monitored by pheromone traps, baited with the acetate of (2S,3S,7S)-3,7-<br /> dimethyl-2-pentadeanol and placed at 100 m interval along two perpendicular, 1500 m lines<br /> intersecting the treated area. The trap catch reduction was near 100% during the first month, but<br /> then declined to around 90% during the second month. Mating frequencies were checked by<br /> comparing the sex ratio of the next generation from within and outside the treatment area. No<br /> effect of the treatment on the sex ratio was detected, and the frequency of mated females could be<br /> assumed to be independent of treatment. Alternative hypotheses to explain the failure of<br /> pheromone mating disruption in N. sertifer are discussed.
  • 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 .- 0937-7409. ; 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.
  • Andersson, Johan, et al. (författare)
  • Cardiovascular and respiratory responses to apneas with and without face immersion in exercising humans
  • 2004
  • Ingår i: Journal of applied physiology. - 8750-7587. ; 96:3, s. 1005-1010
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of the diving response on alveolar gas exchange was investigated in 15 subjects. During steady-state exercise (80 W) on a cycle ergometer, the subjects performed 40-s apneas in air and 40-s apneas with face immersion in cold (10degreesC) water. Heart rate decreased and blood pressure increased during apneas, and the responses were augmented by face immersion. Oxygen uptake from the lungs decreased during apnea in air (-22% compared with eupneic control) and was further reduced during apnea with face immersion (-25% compared with eupneic control). The plasma lactate concentration increased from control (11%) after apnea in air and even more after apnea with face immersion (20%), suggesting an increased anaerobic metabolism during apneas. The lung oxygen store was depleted more slowly during apnea with face immersion because of the augmented diving response, probably including a decrease in cardiac output. Venous oxygen stores were probably reduced by the cardiovascular responses. The turnover times of these gas stores would have been prolonged, reducing their effect on the oxygen uptake in the lungs. Thus the human diving response has an oxygen-conserving effect.
  • Andersson, Johan, et al. (författare)
  • Cardiovascular responses to cold water immersions of the forearm and face, and their relationship to apnoea
  • 2000
  • Ingår i: European Journal of Applied Physiology. - 1439-6319. ; 83:6, s. 566-572
  • Tidskriftsartikel (refereegranskat)abstract
    • Apnoea as well as cold stimulation of the face or the extremities elicits marked cardiovascular reflexes in humans. The purpose of this study was to investigate whether forearm immersion in cold water has any effect on the cardiovascular responses to face immersion and apnoea. We recorded cardiovascular responses to cold-water immersions of the forearm and face in 19 (part I) and 23 subjects (part II). The experimental protocol was divided in two parts, each part containing four tests: I1, forearm immersion during eupnoea; I2, face immersion during eupnoea; I3, forearm and face immersion during eupnoea; I4, face immersion during apnoea; II1, apnoea without immersion; II2, forearm immersion during apnoea; II3, face immersion during apnoea; and II4, forearm and face immersion during apnoea. The water temperature was 9–11?°C. Cold-water immersion of either the forearm or face was enough to elicit the most pronounced thermoregulatory vasoconstriction during both eupnoea and apnoea. During eupnoea, heart rate responses to forearm immersion (3% increase) and face immersion (9% decrease) were additive during concurrent stimulation (3% decrease). During apnoea, the heart rate responses were not affected by the forearm immersion. The oxygen-conserving diving response seems to dominate over thermoregulatory responses in the threat of asphyxia. During breathing, however, the diving response serves no purpose and does not set thermoregulatory adjustments aside
  • Andersson, Johan, et al. (författare)
  • Diving response and arterial oxygen saturation during apnea and exercise in breath-hold divers
  • 2002
  • Ingår i: Journal of applied physiology. - 8750-7587. ; 93:3, s. 882-886
  • Tidskriftsartikel (refereegranskat)abstract
    • This study addressed the effects of apnea in air and apnea with face immersion in cold water (10°C) on the diving response and arterial oxygen saturation during dynamic exercise. Eight trained breath-hold divers performed steady-state exercise on a cycle ergometer at 100 W. During exercise, each subject performed 30-s apneas in air and 30-s apneas with face immersion. The heart rate and arterial oxygen saturation decreased and blood pressure increased during the apneas. Compared with apneas in air, apneas with face immersion augmented the heart rate reduction from 21 to 33% (P &lt; 0.001) and the blood pressure increase from 34 to 42% (P &lt; 0.05). The reduction in arterial oxygen saturation from eupneic control was 6.8% during apneas in air and 5.2% during apneas with face immersion (P &lt; 0.05). The results indicate that augmentation of the diving response slows down the depletion of the lung oxygen store, possibly associated with a larger reduction in peripheral venous oxygen stores and increased anaerobiosis. This mechanism delays the fall in alveolar and arterial Po2 and, thereby, the development of hypoxia in vital organs. Accordingly, we conclude that the human diving response has an oxygen-conserving effect during exercise.
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