| 1. |
- Mathews, G. S., et al.
(author)
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GAS in Protoplanetary Systems (GASPS) I. First results
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L127
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Journal article (peer-reviewed)abstract
- Context. Circumstellar discs are ubiquitous around young stars, but rapidly dissipate their gas and dust on timescales of a few Myr. The Herschel Space Observatory allows for the study of the warm disc atmosphere, using far-infrared spectroscopy to measure gas content and excitation conditions, and far-IR photometry to constrain the dust distribution. Aims. We aim to detect and characterize the gas content of circumstellar discs in four targets as part of the Herschel science demonstration phase. Methods. We carried out sensitive medium resolution spectroscopy and high sensitivity photometry at gimel similar to 60-190 mu m using the Photodetector Array Camera and Spectrometer instrument on the Herschel Space Observatory. Results. We detect [OI] 63 mu m emission from the young stars HD 169142, TW Hydrae, and RECX 15, but not HD 181327. No other lines, including [CII] 158 and [OI] 145, are significantly detected. All four stars are detected in photometry at 70 and 160 mu m. Extensive models are presented in associated papers.
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| 2. |
- Meeus, G., et al.
(author)
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Gas in the protoplanetary disc of HD 169142: Herschel's view
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L124
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Journal article (peer-reviewed)abstract
- In an effort to simultaneously study the gas and dust components of the disc surrounding the young Herbig Ae star HD 169142, we present far-IR observations obtained with the PACS instrument onboard the Herschel Space Observatory. This work is part of the open time key program GASPS, which is aimed at studying the evolution of protoplanetary discs. To constrain the gas properties in the outer disc, we observed the star at several key gas-lines, including [OI] 63.2 and 145.5 mu m, [CII] 157.7 mu m, CO 72.8 and 90.2 mu m, and o-H2O 78.7 and 179.5 mu m. We only detect the [OI] 63.2 mu m line in our spectra, and derive upper limits for the other lines. We complement our data set with PACS photometry and (CO)-C-12/13 data obtained with the Submillimeter Array. Furthermore, we derive accurate stellar parameters from optical spectra and UV to mm photometry. We model the dust continuum with the 3D radiative transfer code MCFOST and use this model as an input to analyse the gas lines with the thermo-chemical code ProDIMo. Our dataset is consistent with a simple model in which the gas and dust are well-mixed in a disc with a continuous structure between 20 and 200 AU, but this is not a unique solution. Our modelling effort allows us to constrain the gas-to-dust mass ratio as well as the relative abundance of the PAHs in the disc by simultaneously fitting the lines of several species that originate in different regions. Our results are inconsistent with a gas-poor disc with a large UV excess; a gas mass of 5.0 +/- 2.0 x 10(-3) M-circle dot is still present in this disc, in agreement with earlier CO observations.
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| 3. |
- Pinte, C., et al.
(author)
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The Herschel view of GAS in Protoplanetary Systems (GASPS) First comparisons with a large grid of models
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L126
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Journal article (peer-reviewed)abstract
- The Herschel GASPS key program is a survey of the gas phase of protoplanetary discs, targeting 240 objects which cover a large range of ages, spectral types, and disc properties. To interpret this large quantity of data and initiate self-consistent analyses of the gas and dust properties of protoplanetary discs, we have combined the capabilities of the radiative transfer code MCFOST with the gas thermal balance and chemistry code ProDiMo to compute a grid of approximate to 300 000 disc models (DENT). We present a comparison of the first Herschel/GASPS line and continuum data with the predictions from the DENT grid of models. Our objective is to test some of the main trends already identified in the DENT grid, as well as to define better empirical diagnostics to estimate the total gas mass of protoplanetary discs. Photospheric UV radiation appears to be the dominant gas-heating mechanism for Herbig stars, whereas UV excess and/or X-rays emission dominates for T Tauri stars. The DENT grid reveals the complexity in the analysis of far-IR lines and the difficulty to invert these observations into physical quantities. The combination of Herschel line observations with continuum data and/or with rotational lines in the (sub-)millimetre regime, in particular CO lines, is required for a detailed characterisation of the physical and chemical properties of circumstellar discs.
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| 4. |
- Thi, W. F., et al.
(author)
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Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya Constraining the disk gas mass
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L125
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Journal article (peer-reviewed)abstract
- Planets are formed in disks around young stars. With an age of similar to 10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel-PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [OI] and [CII] as part of the open-time large program GASPS. We complement this with continuum data and ground-based (12) CO 3-2 and (CO)-C-13 3-2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [OI] line at 63 mu m. The other lines that were observed, [OI] at 145 mu m and [CII] at 157 mu m, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming [(CO)-C-12]/[(CO)-C-13] = 69 suggests a dust mass for grains with radius
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| 5. |
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| 6. |
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| 7. |
- Hodcroft, EB, et al.
(author)
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Evolution, geographic spreading, and demographic distribution of Enterovirus D68
- 2022
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In: PLoS pathogens. - : Public Library of Science (PLoS). - 1553-7374. ; 18:5, s. e1010515-
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Journal article (peer-reviewed)abstract
- Worldwide outbreaks of enterovirus D68 (EV-D68) in 2014 and 2016 have caused serious respiratory and neurological disease. We collected samples from several European countries during the 2018 outbreak and determined 53 near full-length genome (‘whole genome’) sequences. These sequences were combined with 718 whole genome and 1,987 VP1-gene publicly available sequences. In 2018, circulating strains clustered into multiple subgroups in the B3 and A2 subclades, with different phylogenetic origins. Clusters in subclade B3 emerged from strains circulating primarily in the US and Europe in 2016, though some had deeper roots linking to Asian strains, while clusters in A2 traced back to strains detected in East Asia in 2015-2016. In 2018, all sequences from the USA formed a distinct subgroup, containing only three non-US samples. Alongside the varied origins of seasonal strains, we found that diversification of these variants begins up to 18 months prior to the first diagnostic detection during a EV-D68 season. EV-D68 displays strong signs of continuous antigenic evolution and all 2018 A2 strains had novel patterns in the putative neutralizing epitopes in the BC- and DE-loops. The pattern in the BC-loop of the USA B3 subgroup had not been detected on that continent before. Patients with EV-D68 in subclade A2 were significantly older than patients with a B3 subclade virus. In contrast to other subclades, the age distribution of A2 is distinctly bimodal and was found primarily among children and in the elderly. We hypothesize that EV-D68’s rapid evolution of surface proteins, extensive diversity, and high rate of geographic mixing could be explained by substantial reinfection of adults. Better understanding of evolution and immunity across diverse viral pathogens, including EV-D68 and SARS-CoV-2, is critical to pandemic preparedness in the future.
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| 8. |
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| 9. |
- Junker, Robert R., et al.
(author)
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Covariation and phenotypic integration in chemical communication displays : Biosynthetic constraints and eco-evolutionary implications
- 2018
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 220:3, s. 739-749
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Journal article (peer-reviewed)abstract
- Chemical communication is ubiquitous. The identification of conserved structural elements in visual and acoustic communication is well established, but comparable information on chemical communication displays (CCDs) is lacking. We assessed the phenotypic integration of CCDs in a meta-analysis to characterize patterns of covariation in CCDs and identified functional or biosynthetically constrained modules. Poorly integrated plant CCDs (i.e. low covariation between scent compounds) support the notion that plants often utilize one or few key compounds to repel antagonists or to attract pollinators and enemies of herbivores. Animal CCDs (mostly insect pheromones) were usually more integrated than those of plants (i.e. stronger covariation), suggesting that animals communicate via fixed proportions among compounds. Both plant and animal CCDs were composed of modules, which are groups of strongly covarying compounds. Biosynthetic similarity of compounds revealed biosynthetic constraints in the covariation patterns of plant CCDs. We provide a novel perspective on chemical communication and a basis for future investigations on structural properties of CCDs. This will facilitate identifying modules and biosynthetic constraints that may affect the outcome of selection and thus provide a predictive framework for evolutionary trajectories of CCDs in plants and animals.
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| 10. |
- Khaling, Eliezer, et al.
(author)
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Ozone affects growth and development of Pieris brassicae on the wild host plant Brassica nigra
- 2015
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In: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 199, s. 119-129
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Journal article (peer-reviewed)abstract
- When plants are exposed to ozone they exhibit changes in both primary and secondary metabolism, which may affect their interactions with herbivorous insects. Here we investigated the performance and preferences of the specialist herbivore Pieris brassicae on the wild plant Brassica nigra under elevated ozone conditions. The direct and indirect effects of ozone on the plant-herbivore system were studied. In both cases ozone exposure had a negative effect on P. brassicae development. However, in dual-choice tests larvae preferentially consumed plant material previously fumigated with the highest concentration tested, showing a lack of correlation between larval preference and performance on ozone exposed plants. Metabolomic analysis of leaf material subjected to combinations of ozone and herbivore-feeding, and focussing on known defence metabolites, indicated that P. brassicae behaviour and performance were associated with ozone-induced alterations to glucosinolate and phenolic pools.
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| 11. |
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| 12. |
- Papazian, Stefano, 1986-, et al.
(author)
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Herbivore-Induced Metabolic Responses in Brassica nigra are Shaped by Leaf Ontogeny
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Other publication (other academic/artistic)abstract
- In order to defend, plants rely on quick metabolic reconfigurations. Here weinvestigated plant herbivore-induced responses asking: 1) how exposure to methyljasmonate(MeJA) and herbivory alter plant defence and growth metabolism, and 2)are herbivore-induced responses concentrated in tissues with higher fitness value, aspredicted by the optimal defence (OD) theory? We analysed the leaf metabolome of black mustard (B. nigra) in response to MeJAand/or feeding by specialist caterpillars of the large white cabbage butterfly (Pierisbrassicae). Shifts in defence-related (secondary) and growth-related (primary)metabolites were initially evaluated on fully expanded mature leaves and thenfollowed across leaf ontogeny. MeJA enhanced herbivore induced-responses and increased the plant resistanceagainst sequential herbivory. Responses were focused in young leaves andcharacterized by changes in defence- (glucosinolates, phenolics) and growth- (aminoacids, sugars, organic acids) metabolism, including asymmetric accumulation ofcentral tricarboxylic acid cycle (TCA) intermediates. MeJA application enhanced the plant resistance towards herbivory and, consistentlywith the OD theory, herbivore-induced responses were prioritized in young leaves.However, shifts in the plant were not limited to higher defences but affected growthmetabolism including regulation of energy pathways and increased leaf senescence.These effects deserve attention by future ecological and applied research on plantinsectinteractions.
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| 13. |
- Papazian, Stefano, 1986-, et al.
(author)
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Leaf metabolic signatures induced by real and simulated herbivory in black mustard (Brassica nigra)
- 2019
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In: Metabolomics. - : Springer. - 1573-3882 .- 1573-3890. ; 15:10
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Journal article (peer-reviewed)abstract
- Introduction The oxylipin methyl jasmonate (MeJA) is a plant hormone active in response signalling and defence against herbivores. Although MeJA is applied experimentally to mimic herbivory and induce plant defences, its downstream effects on the plant metabolome are largely uncharacterized, especially in the context of primary growth and tissue-specificity of the response. Objectives We investigated the effects of MeJA-simulated and real caterpillar herbivory on the foliar metabolome of the wild plant Brassica nigra and monitored the herbivore-induced responses in relation to leaf ontogeny. Methods As single or multiple herbivory treatments, MeJA- and mock-sprayed plants were consecutively exposed to caterpillars or left untreated. Gas chromatography (GC) and liquid chromatography (LC) time-of-flight mass-spectrometry (TOF-MS) were combined to analyse foliar compounds, including central primary and specialized defensive plant metabolites. Results Plant responses were stronger in young leaves, which simultaneously induced higher chlorophyll levels. Both MeJA and caterpillar herbivory induced similar, but not identical, accumulation of tricarboxylic acids (TCAs), glucosinolates (GSLs) and phenylpropanoids (PPs), but only caterpillar feeding led to depletion of amino acids. MeJA followed by caterpillars caused higher induction of defence compounds, including a three-fold increase in the major defence compound allyl-GSL (sinigrin). When feeding on MeJA-treated plants, caterpillars gained less weight indicative of the reduced host-plant quality and enhanced resistance. Conclusions The metabolomics approach showed that plant responses induced by herbivory extend beyond the regulation of defence metabolism and are tightly modulated throughout leaf development. This leads to a new understanding of the plant metabolic potential that can be exploited for future plant protection strategies.
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| 14. |
- Persson, Carina, 1964, et al.
(author)
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Water and ammonia abundances in S140 with the Odin satellite
- 2009
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 2:494, s. 637-646
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Journal article (peer-reviewed)abstract
- We investigate the effect of the physical environment on water and ammonia abundances across the S140 photodissociation region (PDR) with an embedded outflow.We used the Odin satellite to obtain strip maps of the ground-state rotational transitions of ortho-water and ortho-ammonia, as well as CO(5-4) and 13co(5-4) across the PDR, and H_2^18O in the central position. A physi-chemicalinhomogeneous PDR model was used to compute the temperature and abundance distributions for water, ammonia, and CO. A multi-zone escape probability method then calculated the level populations and intensity distributions. These results are compared to a homogeneous model computed with an enhanced version of the RADEX code.H_2O, NH_3, and ^13CO show emission from an extended PDR with a narrow line width of ~3 km/s. Like CO, the water line profile is dominated by outflow emission, but mainly in the red wing. Even though CO shows strong self-absorption, no signs of self-absorption are seen in the water line. The H_2^18O molecule is not detected.The PDR model suggests that the water emission arises mainly from the surfaces of optically thick, high-density clumps with n(H_2)>10^6 cm^-3 and a clump water abundance, with respect to H_2, of 5*10^-8. The mean water abundance in the PDR is 5*10^-9 and between ~4*10^-8 - 4*10^-7 in the outflow derived from a simple two-level approximation.The RADEX model points to a somewhat higher average PDR water abundance of 1*10^-8. At low temperatures deep in the cloud, the water emission is weaker, likely due to adsorption onto dust grains, while ammonia is still abundant. Ammonia is also observed in the extended clumpy PDR, likely from the same high density and warm clumps as water. The average ammonia abundance is about the same as for water: 4*10^-9 and 8*10^-9 given by the PDR model and RADEX, respectively. The differences between the models most likely arise from uncertainties in density,beam-filling, and volume-filling of clumps. The similarity of water and ammonia PDR emission is also seen in the almost identical line profiles observed close to the bright rim. Around the central position, ammonia also shows some outflow emission, although weaker than water in the red wing. Predictions of the H_2O 1(1,0)-1(0,1) and 1(1,1)-0(0,0) antenna temperatures across the PDR are estimated with our PDR model for the forthcoming observations with the Herschel Space Observatory.
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| 15. |
- Van Puyvelde, L., et al.
(author)
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Photoluminescence investigation of Cu2ZnSnS4 thin film solar cells
- 2015
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 582, s. 146-150
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Journal article (peer-reviewed)abstract
- Cu2ZnSnS4 (CZTS) is a promising absorber for thin film solar cells which is non-toxic and consists of only abundant elements. In order to achieve higher solar cell efficiencies for this material, a better understanding about its defect structure is necessary. In this paper photoluminescence (PL) from sputtered CZTS thin film solar cells which differ in buffer layer thickness was studied. In the PL spectra three broad peaks could be distinguished between 0.9 and 1.3 eV. The PL measurements as a function of temperature and excitation power density revealed the presence of potential fluctuations. The separations between the band edge of the photoluminescence excitation signal and the PL emission peaks are large, which indicates that PL involves trapping of carriers by deep-level defects.
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