| 1. |
- Abelev, Betty, et al.
(författare)
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Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
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| 2. |
- Abelev, Betty, et al.
(författare)
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Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
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Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
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| 3. |
- Abelev, Betty, et al.
(författare)
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Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
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Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
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| 4. |
- Farnocchia, Davide, et al.
(författare)
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International Asteroid Warning Network Timing Campaign: 2019 XS
- 2022
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Ingår i: The Planetary Science Journal. - : Institute of Physics Publishing (IOPP). - 2632-3338. ; 3:7
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Tidskriftsartikel (refereegranskat)abstract
- As part of the International Asteroid Warning Network's observational exercises, we conducted a campaign to observe near-Earth asteroid 2019 XS around its close approach to Earth on 2021 November 9. The goal of the campaign was to characterize errors in the observation times reported to the Minor Planet Center, which become an increasingly important consideration as astrometric accuracy improves and more fast-moving asteroids are observed. As part of the exercise, a total of 957 astrometric observations of 2019 XS during the encounter were reported and subsequently were analyzed to obtain the corresponding residuals. While the timing errors are typically smaller than 1 s, the reported times appear to be negatively biased, i.e., they are generally earlier than they should be. We also compared the observer-provided position uncertainty with the cross-track residuals, which are independent of timing errors. A large fraction of the estimated uncertainties appear to be optimistic, especially when <0 2. We compiled individual reports for each observer to help identify and remove the root cause of any possible timing error and improve the uncertainty quantification process. We suggest possible sources of timing errors and describe a simple procedure to derive reliable, conservative position uncertainties.
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| 5. |
- Farnocchia, Davide, et al.
(författare)
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The Second International Asteroid Warning Network Timing Campaign: 2005 LW3
- 2023
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Ingår i: The Planetary Science Journal. - : Institute of Physics (IOP). - 2632-3338. ; 4:11
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Tidskriftsartikel (refereegranskat)abstract
- The Earth close approach of near-Earth asteroid 2005 LW3 on 2022 November 23 represented a good opportunity for a second observing campaign to test the timing accuracy of astrometric observation. With 82 participating stations, the International Asteroid Warning Network collected 1046 observations of 2005 LW3 around the time of the close approach. Compared to the previous timing campaign targeting 2019 XS, some individual observers were able to significantly improve the accuracy of their reported observation times. In particular, U.S. surveys achieved good timing performance. However, no broad, systematic improvement was achieved compared to the previous campaign, with an overall negative bias persisting among the different observers. The calibration of observing times and the mitigation of timing errors should be important future considerations for observers and orbit computers, respectively.
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| 6. |
- Kurepin, Leonid V., et al.
(författare)
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Role of CBFs as Integrators of Chloroplast Redox, Phytochrome and Plant Hormone Signaling during Cold Acclimation
- 2013
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 14:6, s. 12729-12763
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Forskningsöversikt (refereegranskat)abstract
- Cold acclimation of winter cereals and other winter hardy species is a prerequisite to increase subsequent freezing tolerance. Low temperatures upregulate the expression of C-repeat/dehydration-responsive element binding transcription factors (CBF/DREB1) which in turn induce the expression of COLD-REGULATED (COR) genes. We summarize evidence which indicates that the integration of these interactions is responsible for the dwarf phenotype and enhanced photosynthetic performance associated with cold-acclimated and CBF-overexpressing plants. Plants overexpressing CBFs but grown at warm temperatures mimic the cold-tolerant, dwarf, compact phenotype; increased photosynthetic performance; and biomass accumulation typically associated with cold-acclimated plants. In this review, we propose a model whereby the cold acclimation signal is perceived by plants through an integration of low temperature and changes in light intensity, as well as changes in light quality. Such integration leads to the activation of the CBF-regulon and subsequent upregulation of COR gene and GA 2-oxidase (GA2ox) expression which results in a dwarf phenotype coupled with increased freezing tolerance and enhanced photosynthetic performance. We conclude that, due to their photoautotrophic nature, plants do not rely on a single low temperature sensor, but integrate changes in light intensity, light quality, and membrane viscosity in order to establish the cold-acclimated state. CBFs appear to act as master regulators of these interconnecting sensing/signaling pathways.
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| 7. |
- Huner, Norman P A, et al.
(författare)
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Photoprotection of Photosystem II: Reaction center quenching versus antenna quenching
- 2006
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Ingår i: Photoprotection, Photoinhibition, Gene Regulation and Environment. - : Springer. - 9781402035647 ; , s. 155-174
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Photoprotection, Photoinhibition, Gene Regulation, and Environment examines the processes whereby plants monitor environmental conditions and orchestrate their response to change, an ability paramount to the life of all plants. "Excess light", absorbed by the light-harvesting systems of photosynthetic organisms, is an integrative indicator of the environment, communicating the presence of intense light and any conditions unfavorable for growth and photosynthesis. Key plant responses are photoprotection and photoinhibition. In this volume, the dual role of photoprotective responses in the preservation of leaf integrity and in redox signaling networks modulating stress acclimation, growth, and development is addressed. In addition, the still unresolved impact of photoinhibition on plant survival and productivity is discussed. Specific topics include dissipation of excess energy via thermal and other pathways, scavenging of reactive oxygen by antioxidants, proteins key to photoprotection and photoinhibition, peroxidation of lipids, as well as signaling by reactive oxygen, lipid-derived messengers, and other messengers that modulate gene expression. Approaches include biochemical, physiological, genetic, molecular, and field studies, addressing intense visible and ultraviolet light, winter conditions, nutrient deficiency, drought, and salinity. This book is directed toward advanced undergraduate students, graduate students, and researchers interested in Plant Ecology, Stress Physiology, Plant Biochemistry, Integrative Biology, and Photobiology.
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| 8. |
- Ivanov, Alexander G, et al.
(författare)
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Acclimation to temperature and irradiance modulates PSII charge recombination.
- 2006
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793. ; 580:11, s. 2797-802
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Tidskriftsartikel (refereegranskat)abstract
- Acclimation of wild type and the chlorina F2 mutant of barley to either high light or low temperature results in a 2- to 3-fold increase in non-photochemical quenching which occurred independently of either energy-dependent quenching (qE), xanthophyll cycle-mediated antenna quenching or state transitions. Results of in vivo thermoluminescence measurements used to address this conundrum indicated that excitation pressure regulates the temperature gap for Click to view the MathML source and Click to view the MathML source charge recombinations within photosystem II reaction centers. This is discussed in terms of photoprotection through non-radiative charge recombination.
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| 9. |
- Ivanov, Alexander G., et al.
(författare)
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The decreased PG content of pgp1 inhibits PSI photochemistry and limits reaction center and light-harvesting polypeptide accumulation in response to cold acclimation
- 2022
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Ingår i: Planta. - : Springer. - 0032-0935 .- 1432-2048. ; 255:2
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Tidskriftsartikel (refereegranskat)abstract
- Main conclusion: Decreased PG constrains PSI activity due to inhibition of transcript and polypeptide abundance of light-harvesting and reaction center polypeptides generating a reversible, yellow phenotype during cold acclimation of pgp1.Cold acclimation of the Arabidopsis pgp1 mutant at 5 °C resulted in a pale-yellow phenotype with abnormal chloroplast ultrastructure compared to its green phenotype upon growth at 20 °C despite a normal cold-acclimation response at the transcript level. In contrast, wild type maintained its normal green phenotype and chloroplast ultrastructure irrespective of growth temperature. In contrast to cold acclimation of WT, growth of pgp1 at 5 °C limited the accumulation of Lhcbs and Lhcas assessed by immunoblotting. However, a novel 43 kD polypeptide of Lhcb1 as well as a 29 kD polypeptide of Lhcb3 accumulated in the soluble fraction which was absent in the thylakoid membrane fraction of cold-acclimated pgp1 which was not observed in WT. Cold acclimation of pgp1 destabilized the Chl–protein complexes associated with PSI and predisposed energy distribution in favor of PSII rather than PSI compared to the WT. Functionally, in vivo PSI versus PSII photochemistry was inhibited in cold-acclimated pgp1 to a greater extent than in WT relative to controls. Greening of the pale-yellow pgp1 was induced when cold-acclimated pgp1 was shifted from 5 to 20 °C which resulted in a marked decrease in excitation pressure to a level comparable to WT. Concomitantly, Lhcbs and Lhcas accumulated with a simultaneous decrease in the novel 43 and 29kD polypeptides. We conclude that the reduced levels of phosphatidyldiacylglycerol in the pgp1 limit the capacity of the mutant to maintain the structure and function of its photosynthetic apparatus during cold acclimation. Thus, maintenance of normal thylakoid phosphatidyldiacylglycerol levels is essential to stabilize the photosynthetic apparatus during cold acclimation.
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| 10. |
- Kattge, Jens, et al.
(författare)
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TRY plant trait database - enhanced coverage and open access
- 2020
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Ingår i: Global Change Biology. - : Wiley-Blackwell. - 1354-1013 .- 1365-2486. ; 26:1, s. 119-188
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Tidskriftsartikel (refereegranskat)abstract
- Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
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| 11. |
- Kurepin, Leonid V., et al.
(författare)
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Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature
- 2018
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 41:6, s. 1331-1345
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Tidskriftsartikel (refereegranskat)abstract
- High latitude forests will experience large changes in temperature and CO2 concentrations this century. We evaluated the effects of future climate conditions on 2 dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to 3 seasons of ambient (430 ppm) or elevated CO2 (750 ppm) and ambient temperatures, a + 4 degrees C warming or a + 8 degrees C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO2 assimilation rates (Anet), and acclimated dark respiration (Rdark). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of Anet decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of Rdark was weak. Elevated CO2 tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8 degrees C, high CO2 treatment produced fewer buds than they had 3 years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.
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| 12. |
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| 13. |
- Kurepin, Leonid V., et al.
(författare)
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Stress-related hormones and glycinebetaine interplay in protection of photosynthesis under abiotic stress conditions
- 2015
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Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 126:2-3, s. 221-235
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Forskningsöversikt (refereegranskat)abstract
- Plants subjected to abiotic stresses such as extreme high and low temperatures, drought or salinity, often exhibit decreased vegetative growth and reduced reproductive capabilities. This is often associated with decreased photosynthesis via an increase in photoinhibition, and accompanied by rapid changes in endogenous levels of stress-related hormones such as abscisic acid (ABA), salicylic acid (SA) and ethylene. However, certain plant species and/or genotypes exhibit greater tolerance to abiotic stress because they are capable of accumulating endogenous levels of the zwitterionic osmolyte-glycinebetaine (GB). The accumulation of GB via natural production, exogenous application or genetic engineering, enhances plant osmoregulation and thus increases abiotic stress tolerance. The final steps of GB biosynthesis occur in chloroplasts where GB has been shown to play a key role in increasing the protection of soluble stromal and lumenal enzymes, lipids and proteins, of the photosynthetic apparatus. In addition, we suggest that the stress-induced GB biosynthesis pathway may well serve as an additional or alternative biochemical sink, one which consumes excess photosynthesis-generated electrons, thus protecting photosynthetic apparatus from overreduction. Glycinebetaine biosynthesis in chloroplasts is up-regulated by increases in endogenous ABA or SA levels. In this review, we propose and discuss a model describing the close interaction and synergistic physiological effects of GB and ABA in the process of cold acclimation of higher plants.
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| 14. |
- Pozina, Galia, et al.
(författare)
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Nonlinear behavior of the emission in the periodic structure of InAs monolayers embedded in a GaAs matrix
- 2017
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Ingår i: Physica status solidi. B, Basic research. - : WILEY-V C H VERLAG GMBH. - 0370-1972 .- 1521-3951. ; 254:4
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (TRPL) measurements performed at different temperatures for the Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in a GaAs matrix. TRPL data reveal an appearance of the additional superradiant (SR) mode originated from coherent collective interaction of QWs. The SR mode is not manifested in the case if a small number of QWs is excited, then only an exciton emission related to the InAs QWs dominates the PL spectrum. The SR mode demonstrates a superlinear dependence of the intensity and radiative decay rate on the excitation power and its intensity increases at elevated temperatures compared to the excitonic emission. The photoluminescence delay time is much shorter for the SR mode indicating that the relaxation of hot excitons can occur via stimulated scattering processes. The specific behavior of the SR emission can have a strong potential for different applications such as optical logic devices, superluminescent diodes, optical switches, and low-threshold lasers. Time-resolved photoluminescence image at low temperature for the Bragg structure consisting of InAs monolayer-based quantum wells (inset).
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| 15. |
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| 16. |
- Savitch, Leonid V., et al.
(författare)
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Regulation of energy partitioning and alternative electron transport pathways during cold acclimation of lodgepole pine is oxygen dependent
- 2010
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Ingår i: Plant and Cell Physiology. - : Oxford University Press (OUP). - 0032-0781 .- 1471-9053. ; 51:9, s. 1555-1570
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Tidskriftsartikel (refereegranskat)abstract
- Second year needles of Lodgepole pine (Pinus contorta L.) were exposed for 6 weeks to either simulated control summer [summer; 25C/250 photon flux denisty (PFD)], autumn (autumn; 15C/250 PFD) or winter conditions (winter; 5C/250 PFD). We report that the proportion of linear electron transport utilized in carbon assimilation (ETRCO2) was 40 lower in both autumn and winter pine when compared with the summer pine. In contrast, the proportion of excess photosynthetic linear electron transport (ETRexcess) not used for carbon assimilation within the total ETRJf increased by 30 in both autumn and winter pine. In autumn pine acclimated to 15C, the increased amounts of excess electrons were directed equally to 21kPa O-2-dependent and 2kPa O-2-dependent alternative electron transport pathways and the fractions of excitation light energy utilized by PSII photochemistry ((PSII)), thermally dissipated through (NPQ) and dissipated by additional quenching mechanism(s) ((f,D)) were similar to those in summer pine. In contrast, in winter needles acclimated to 5C, 60 of photosynthetically generated excess electrons were utilized through the 2kPa O-2-dependent electron sink and only 15 by the photorespiratory (21kPa O-2) electron pathway. Needles exposed to winter conditions led to a 3-fold lower (PSII), only a marginal increase in (NPQ) and a 2-fold higher (f,D), which was O-2 dependent compared with the summer and autumn pine. Our results demonstrate that the employment of a variety of alternative pathways for utilization of photosynthetically generated electrons by Lodgepole pine depends on the acclimation temperature. Furthermore, dissipation of excess light energy through constitutive non-photochemical quenching mechanisms is O-2 dependent.
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| 17. |
- Sylantyev, Sergiy, et al.
(författare)
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Electric fields due to synaptic currents sharpen excitatory transmission
- 2008
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 319:5871, s. 1845-1849
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Tidskriftsartikel (refereegranskat)abstract
- The synaptic response waveform, which determines signal integration properties in the brain, depends on the spatiotemporal profile of neurotransmitter in the synaptic cleft. Here, we show that electrophoretic interactions between AMPA receptor–mediated excitatory currents and negatively charged glutamate molecules accelerate the clearance of glutamate from the synaptic cleft, speeding up synaptic responses. This phenomenon is reversed upon depolarization and diminished when intracleft electric fields are weakened through a decrease in the AMPA receptor density. In contrast, the kinetics of receptor-mediated currents evoked by direct application of glutamate are voltage-independent, as are synaptic currents mediated by the electrically neutral neurotransmitter GABA. Voltage-dependent temporal tuning of excitatory synaptic responses may thus contribute to signal integration in neural circuits.
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