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Sökning: WFRF:(Agrell P)

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1.
  • Agrell, Erik, 1965, et al. (författare)
  • Roadmap of optical communications
  • 2016
  • Ingår i: Journal of Optics. - : IOP Publishing. - 2040-8978 .- 2040-8986. ; 18:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Lightwave communications is a necessity for the information age. Optical links provide enormous bandwidth, and the optical fiber is the only medium that can meet the modern society's needs for transporting massive amounts of data over long distances. Applications range from global high-capacity networks, which constitute the backbone of the internet, to the massively parallel interconnects that provide data connectivity inside datacenters and supercomputers. Optical communications is a diverse and rapidly changing field, where experts in photonics, communications, electronics, and signal processing work side by side to meet the ever-increasing demands for higher capacity, lower cost, and lower energy consumption, while adapting the system design to novel services and technologies. Due to the interdisciplinary nature of this rich research field, Journal of Optics has invited 16 researchers, each a world-leading expert in their respective subfields, to contribute a section to this invited review article, summarizing their views on state-of-the-art and future developments in optical communications.
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2.
  • Agrell, Jep, et al. (författare)
  • Combined effects of elevated CO2 and herbivore damage on alfalfa and cotton
  • 2004
  • Ingår i: Journal of Chemical Ecology. - 1573-1561. ; 30:11, s. 2309-2324
  • Tidskriftsartikel (refereegranskat)abstract
    • We examined herbivore-induced responses of alfalfa (Medicago sativa) and cotton (Gossypium hirsutum) under different CO2 conditions. Plants were grown under ambient (350 ppm) or elevated (700 ppm) CO2 levels, and were either damaged or undamaged by Spodoptera littoralis larvae. At harvest, growth of undamaged (control) plants was determined, and foliar chemical composition of both undamaged and damaged plants was analyzed. Cotton grew faster overall and showed a greater increase in growth in response to CO2 enrichment than did alfalfa. Elevated CO2 levels increased starch and decreased nitrogen levels in damaged alfalfa and undamaged cotton plants. Alfalfa saponin levels were significantly increased by elevated CO2 and damage. Regarding specific saponins, medicagenic acid bidesmoside (3GlcA,28AraRhaXyl medicagenate) concentrations were reduced by high CO2, whereas zanhic acid tridesmoside (3GlcGlcGlc,23Ara,28AraRhaXylApi Za) levels were unaffected by the treatments. Soyasaponin I (3GlcAGalRha soyasapogenol B) was only detected in minute amounts. Alfalfa flavonoid analyses showed that total flavonoid levels were similar between treatments, although free apigenin increased and apigenin glucoside (7-O-[2-O-feruloyl-beta-D-glucuronopyranozyl (1-->2)-O-beta-D-glucuronopyranozyl]-4'-O-beta-D-glucuronopyranozide apigenin) decreased in CO2-enriched plants. In cotton, herbivore damage increased levels of total terpenoid aldehydes, gossypol, hemigossypolone, the heliocides H1 and H4, but not H2 and H3, whereas CO2 enrichment had no effect. These results demonstrate that combined effects of CO2 and herbivore damage vary between plant species, which has implications for the competitive balance within plant communities.
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3.
  • Agrell, Jep, et al. (författare)
  • Elevated CO2 levels and herbivore damage alter host plant preferences
  • 2006
  • Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 112:1, s. 63-72
  • Tidskriftsartikel (refereegranskat)abstract
    • Interactions between the moth Spodoptera littoralis and two of its host plants, alfalfa (Medicago sativa) and cotton (Gossypium hirsutum) were examined, using plants grown under ambient (350 ppm) and elevated (700 ppm) CO2 conditions. To determine strength and effects of herbivore-induced responses assays were performed with both undamaged (control) and herbivore damaged plants. CO2 and damage effects on larval host plant preferences were determined through dual-choice bioassays. In addition, larvae were reared from hatching to pupation on experimental foliage to examine effects on larval growth and development. When undamaged plants were used S. littoralis larvae in consumed more cotton than alfalfa, and CO2 enrichment caused a reduction in the preference for cotton. With damaged plants larvae consumed equal amounts of the two plant species (ambient CO2 conditions), but CO2 enrichment strongly shifted preferences towards cotton, which was then consumed three times more than alfalfa. Complementary assays showed that elevated CO2 levels had no effect on the herbivore-induced responses of cotton, whereas those of alfalfa were significantly increased. Larval growth was highest for larvae fed undamaged cotton irrespectively of CO2 level, and lowest for larvae on damaged alfalfa from the high CO2 treatment. Development time increased on damaged cotton irrespectively of CO2 treatment, and on damaged alfalfa in the elevated CO2 treatment. These results demonstrate that elevated CO2 levels can cause insect herbivores to alter host plant preferences, and that effects on herbivore-induced responses may be a key mechanism behind these processes. Furthermore, since the insects were shown to avoid foliage that reduced their physiological performance, our data suggest that behavioural host plant shifts result in partial escape from negative consequences of feeding on high CO2 foliage. Thus, CO2 enrichment can alter both physiology and behaviour of important insect herbivores, which in turn may to impact plant biodiver
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4.
  • Puttnam, Benjamin, et al. (författare)
  • High-capacity MCF transmission with wideband comb
  • 2017
  • Ingår i: Optics InfoBase Conference Papers. - 2162-2701. ; Part F40-OFC 2017, s. M2J.4-
  • Konferensbidrag (refereegranskat)abstract
    • We describe experiments combining high core-count, homogeneous single-mode multicore fibers with a wideband comb for high-capacity transmission without high-order MIMO reception and demonstrate wideband transmission with coded modulation up to 12,300 km.
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5.
  • Agrell, Erik, 1965, et al. (författare)
  • Roadmap on optical communications
  • 2024
  • Ingår i: Journal of Optics. - 2040-8978 .- 2040-8986. ; 26:9
  • Forskningsöversikt (refereegranskat)abstract
    • The Covid-19 pandemic showed forcefully the fundamental importance broadband data communication and the internet has in our society. Optical communications forms the undisputable backbone of this critical infrastructure, and it is supported by an interdisciplinary research community striving to improve and develop it further. Since the first ‘Roadmap of optical communications’ was published in 2016, the field has seen significant progress in all areas, and time is ripe for an update of the research status. The optical communications area has become increasingly diverse, covering research in fundamental physics and materials science, high-speed electronics and photonics, signal processing and coding, and communication systems and networks. This roadmap describes state-of-the-art and future outlooks in the optical communications field. The article is divided into 20 sections on selected areas, each written by a leading expert in that area. The sections are thematically grouped into four parts with 4-6 sections each, covering, respectively, hardware, algorithms, networks and systems. Each section describes the current status, the future challenges, and development needed to meet said challenges in their area. As a whole, this roadmap provides a comprehensive and unprecedented overview of the contemporary optical communications research, and should be essential reading for researchers at any level active in this field.
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6.
  • Agrell, Jep, et al. (författare)
  • Herbivore-induced responses in alfalfa (Medicago sativa)
  • 2003
  • Ingår i: Journal of Chemical Ecology. - 1573-1561. ; 29:2, s. 303-320
  • Tidskriftsartikel (refereegranskat)abstract
    • The herbivore-induced response of alfalfa (Medicago sativa) was examined through assays with Spodoptera littoralis larvae and analyses of important secondary substances. In food preference experiments, larvae preferred young undamaged alfalfa plants over plants that had been damaged by feeding larvae 5 and 7 days earlier, while no difference in feeding preferences could be detected 1, 9, and 14 days after damage. This suggests a peak in the herbivore induced resistance of alfalfa approximately one week after initial damage. The induced resistance in young plants was also shown to be systemic, while older flowering plants failed to show increased resistance after defoliation. Larvae gained weight slower and had lower pupal mass when fed damaged alfalfa than when fed undamaged alfalfa. Levels of total saponins were increased in foliage of damaged alfalfa, and detailed analyses of specific saponin components revealed doubled concentrations of 3GlcA, 28AraRhaXyl medicagenate (medicagenic acid bidesmoside) and 3GlcAGalRha soyasapogenol B(soyasaponin I). Levels of the flavonoid apigenin (as free aglycone) also were increased in herbivore damaged plants. The herbivore-induced response of alfalfa was significantly weaker than that of cotton: S. littoralis larvae given a choice of undamaged cotton and undamaged alfalfa preferred to feed on cotton, whereas preferences shifted towards alfalfa when plants were damaged.
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7.
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8.
  • Alvarado, A., et al. (författare)
  • Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
  • 2016
  • Ingår i: Journal of Lightwave Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8724 .- 1558-2213. ; 34:2, s. 707-721
  • Tidskriftsartikel (refereegranskat)abstract
    • The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.
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9.
  • Alvarado, A., et al. (författare)
  • Replacing the Soft-Decision FEC Limit Paradigm in the Design of Optical Communication Systems
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:20, s. 4338-4352
  • Tidskriftsartikel (refereegranskat)abstract
    • The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high-order modulation formats, the use of the soft-decision FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis.
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10.
  • Anderson, P, et al. (författare)
  • Within-plant variation in induced defence in developing leaves of cotton plants
  • 2005
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 144:3, s. 427-434
  • Tidskriftsartikel (refereegranskat)abstract
    • According to optimal defence theory (ODT) plants should invest in stronger defence in the most valuable parts, such as reproductive or young tissue. Cotton plants are known to express high resistance to herbivore feeding in the developing leaves at the top of the plant after herbivore-damage. Cotton plants also have developing leaves on side shoots from the nodes all along the plant. This allowed us to investigate within-plant distribution of defence between younger tissues at different locations on the plant. We found that all developing leaves showed increased resistance to feeding by larvae of the generalist moth Spodoptera littoralis after herbivore damage to leaves of the plant. An increase in the concentration of secondary compounds, terpenoid aldehydes, was found in developing leaves both at the top of the plant and on the side shoots. However, the resistance was stronger in the top leaves than in the side shoot leaves, showing that there is intra-plant variation in the induced response between different leaves of the same age. After the initial damage, larval feeding mainly occurred on the older, fully developed true leaves. Furthermore, the herbivore-induced resistance in the developing leaves reduced upward movement of feeding larvae on the plant and reduced the feeding on the upper parts of the plant over a period of at least 6 days. The plant thus benefits from defending all developing leaves by directing feeding to older, less valuable leaves and lower parts of the plant. The observed distribution of defence within cotton plants supports ODT.
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