| 1. |
- Abdalla, H., et al.
(author)
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Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation
- 2021
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In: Journal of Cosmology and Astroparticle Physics. - : Institute of Physics Publishing (IOPP). - 1475-7516. ; :2
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Journal article (peer-reviewed)abstract
- The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for gamma-ray astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of gamma-ray cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of gamma-ray absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z = 2 and to constrain or detect gamma-ray halos up to intergalactic-magnetic-field strengths of at least 0.3 pG. Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from gamma-ray astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of gamma-ray cosmology.
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| 2. |
- Aharonian, F., et al.
(author)
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A deep spectromorphological study of the ϒ-ray emission surrounding the young massive stellar cluster Westerlund 1
- 2022
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In: Astronomy and Astrophysics. - : EPD Sciences. - 0004-6361 .- 1432-0746. ; 666
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Journal article (peer-reviewed)abstract
- Context. Young massive stellar clusters are extreme environments and potentially provide the means for efficient particle acceleration. Indeed, they are increasingly considered as being responsible for a significant fraction of cosmic rays (CRs) that are accelerated within the Milky Way. Westerlund 1, the most massive known young stellar cluster in our Galaxy, is a prime candidate for studying this hypothesis. While the very-high-energy gamma-ray source HESS J1646-458 has been detected in the vicinity of Westerlund 1 in the past, its association could not be firmly identified. Aims. We aim to identify the physical processes responsible for the gamma-ray emission around Westerlund 1 and thus to understand the role of massive stellar clusters in the acceleration of Galactic CRs better. Methods. Using 164 h of data recorded with the High Energy Stereoscopic System (H.E.S.S.), we carried out a deep spectromorphological study of the gamma-ray emission of HESS J1646-458. We furthermore employed H I and CO observations of the region to infer the presence of gas that could serve as target material for interactions of accelerated CRs. Results. We detected large-scale (similar to 2 degrees diameter) gamma-ray emission with a complex morphology, exhibiting a shell-like structure and showing no significant variation with gamma-ray energy. The combined energy spectrum of the emission extends to several tens of TeV, and it is uniform across the entire source region. We did not find a clear correlation of the gamma-ray emission with gas clouds as identified through H I and CO observations. Conclusions. We conclude that, of the known objects within the region, only Westerlund 1 can explain the majority of the gamma-ray emission. Several CR acceleration sites and mechanisms are conceivable and discussed in detail. While it seems clear that Westerlund 1 acts as a powerful particle accelerator, no firm conclusions on the contribution of massive stellar clusters to the flux of Galactic CRs in general can be drawn at this point.
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| 3. |
- Chianella, I, et al.
(author)
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MIP-based solid phase extraction cartridges combined with MIP-based sensors for the detection of microcystin-LR
- 2003
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In: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 18:03-feb, s. 119-127
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Journal article (peer-reviewed)abstract
- Microsystin-LR is one of the most widespread and dangerous toxins produced by the freshwater Cyanobacteria. The contamination of water supplies with microcystin-LR has been reported in several areas around the world and the development of an easy-to-use, rapid, robust and inexpensive sensor for this toxin is urgently required. In this work an artificial receptor for microcystin-LR was synthesised using the technique of molecular imprinting. The composition of the molecularly imprinted polymer (MIP) was optimised using computer modelling. The synthesised polymer was used both as a material for solid-phase extraction (SPE) and as a sensing element in a piezoelectric sensor. Using the combination of SPE followed by detection with a piezoelectric sensor the minimum detectable amount of toxin was 0.35 nM. The use of MIP-SPE provided up to 1000 fold preconcentration, which was more than sufficient for achieving the required detection limit for microcystin-LR in drinking water (I nM). This work is the first example where the same MIP receptor has been used successfully for both SPE and the corresponding sensor. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Chianella, I, et al.
(author)
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Rational design of a polymer specific for microcystin-LR using a computational approach
- 2002
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In: Analytical Chemistry. - : ACS American Chemical Society. - 0003-2700 .- 1520-6882. ; 74:6, s. 1288-1293
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Journal article (peer-reviewed)abstract
- A computational approach for the design of a molecularly imprinted polymer (MIP) specific for Cyanobacterial toxin microcystin-LR is presented. By using molecular modeling software, a virtual library of functional monomers was designed and screened against the target toxin, employed as a template. The monomers giving the highest binding energy were selected and used in a simulated annealing (molecular dynamics) process to investigate their interaction with the template. The stoichiomettic ratio observed from the simulated annealing study was used in MIP preparation for microcystin-LR. The monomers were copolymerized with a cross-linker in the presence of the template. A control (blank) polymer was prepared under the same conditions but in the absence of template. A competitive assay with microcystin-horseradish peroxidase conjugate was optimized and used to evaluate the affinity and cross-reactivity of the polymer. The performance of the artificial receptor was compared to the performance of monoclonal and polyclonal antibodies raised against the toxin. The results indicate that imprinted polymer has affinity and sensitivity comparable to those of polyclonal antibodies (die detection limit for microcystin-LR using the MIP-based assay was found to be 0.1 mug L-1), while superior chemical and thermal stabilities were obtained. Moreover, cross-reactivity to other toxin analogues was very low for the imprinted polymer, in contrast to the results achieved for antibodies. It is anticipated that the polymer designed could be used in assays, sensors, and solid-phase extraction.
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| 5. |
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Highlights from the first year of Odin observations
- 2003
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L39-L46
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Journal article (peer-reviewed)abstract
- Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H218O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR21, S140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; H218O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in~Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 have resulted in very low abundance limits, which are difficult to accomodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'études Spatiales (CNES, France). The Swedish Space Corporation (SSC) has been the prime industrial contractor, and is also responsible for the satellite operation from its Odin Mission Control Centre at SSC in Solna and its Odin Control Centre at ESRANGE near Kiruna in northern Sweden. See also the SNSB Odin web page: http://www.snsb.se/eng_odin_intro.shtml
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| 6. |
- Hobson, NS, et al.
(author)
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Microbial detection
- 1996
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In: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 11:5, s. 455-477
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Research review (peer-reviewed)abstract
- There is a widespread need for commercial instrumentation for the rapid and inexpensive detection of microbial contamination of food, industrial waste water and clinical samples. A large number of detection methods have been developed utilizing the optical, electrochemical, biochemical and physical properties of microorganisms. The need for a device which can produce a rapid, accurate, sensitive, real-time analysis for clinical, industrial and environmental applications has led to considerable progress being achieved in recent years in the development of biosensors for microbial detection. This intense research has resulted in the commercialization of several instruments. Techniques used for the quantification of microorganisms are reviewed under the general categories of non-bioelectrochemical and bioelectrochemical methods.
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| 7. |
- Larsson, B., et al.
(author)
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First NH3 detection of the Orion Bar
- 2003
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L69-L72
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Journal article (peer-reviewed)abstract
- Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J,K) = (1,0) -> (0,0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (\cite{wilson01}). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H2 = 5x 10-9. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor.
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| 8. |
- Liseau, R., et al.
(author)
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First detection of NH3 (10 -> 00) from a low mass cloud core. On the low ammonia abundance of the rho Oph A core
- 2003
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L73-L76
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Journal article (peer-reviewed)abstract
- Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH)= 3 x 10-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8 x 10-10. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation has been the industrial prime contractor. and based on observations collected with the Swedish ESO Submillimeter Telescope, SEST, in La Silla, Chile.
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| 9. |
- Lotierzo, M, et al.
(author)
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Surface plasmon resonance sensor for domoic acid based on grafted imprinted polymer
- 2004
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In: Biosensors & bioelectronics. - : Elsevier Science B.V., Amsterdam.. - 0956-5663 .- 1873-4235. ; 20:2, s. 145-152
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Journal article (peer-reviewed)abstract
- A molecularly imprinted polymer (MIP) film for domoic acid (DA) was synthesised by direct photo-grafting onto a gold chip suitable for a surface plasmon resonance (SPR) based bioanalytical instrument system, the BlAcore 3000(TM). The gold surface was first functionalised with a self-assembled monolayer of 2-mercaptoethylamine and subsequent carbodiimide chemistry was performed for covalent attachment of the photoinitiator, 4,4-azobis(cyanovaleric acid). This ensured that the formation of the MIP thin film, comprising 2-(diethyl amino) ethyl methacrylate as functional monomer and ethylene glycol dimethacrylate as cross-linker, occurred only at the surface level. Optimisation and control over the grafting procedure were achieved using contact angle measurements and atomic force microscope (AFM) imaging. The surface grafting resulted in the formation of thin and homogeneous MIP film with thickness of 40 nm. A competitive binding assay was performed with free DA and its conjugate with horseradish peroxidase, which was used as a refractive label. The sensor was evaluated for its sensitivity, cross-reactivity, and robustness by using a BlAcore 3000(TM). Likewise, monoclonal antibodies acting as natural receptors for the toxin were studied with the same BlAcore system. Results of a comparison between the artificial and natural receptors are reported. In contrast to monoclonal antibodies, the regeneration of MIP chip did not affect its recognition properties and continuous measurement was possible over a period of at least 2 months. (C) 2004 Elsevier B.V. All rights reserved.
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| 10. |
- Olofsson, Henrik, 1972, et al.
(author)
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Odin water mapping in the Orion KL region
- 2003
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L47-L54
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Journal article (peer-reviewed)abstract
- New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60\arcsec-110\arcsec. The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near (or ``blue'') part of the outflow (and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Études Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.
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