| 1. |
- Fomalont, E. B., et al.
(författare)
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THE 2014 ALMA LONG BASELINE CAMPAIGN: AN OVERVIEW
- 2015
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 808:1
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Tidskriftsartikel (refereegranskat)abstract
- A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to similar to 15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at similar to 350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.
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| 2. |
- André, Ph., et al.
(författare)
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Probing the cold magnetised Universe with SPICA-POL (B-BOP)
- 2019
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Ingår i: Publications Astronomical Society of Australia. - : Cambridge University Press (CUP). - 1323-3580 .- 1448-6083. ; 36
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Forskningsöversikt (refereegranskat)abstract
- Space Infrared Telescope for Cosmology and Astrophysics (SPICA), the cryogenic infrared space telescope recently pre-selected for a 'Phase A' concept study as one of the three remaining candidates for European Space Agency (ESA's) fifth medium class (M5) mission, is foreseen to include a far-infrared polarimetric imager [SPICA-POL, now called B-fields with BOlometers and Polarizers (B-BOP)], which would offer a unique opportunity to resolve major issues in our understanding of the nearby, cold magnetised Universe. This paper presents an overview of the main science drivers for B-BOP, including high dynamic range polarimetric imaging of the cold interstellar medium (ISM) in both our Milky Way and nearby galaxies. Thanks to a cooled telescope, B-BOP will deliver wide-field 100-350 mu m images of linearly polarised dust emission in Stokes Q and U with a resolution, signal-to-noise ratio, and both intensity and spatial dynamic ranges comparable to those achieved by Herschel images of the cold ISM in total intensity (Stokes I). The B-BOP 200 mu m images will also have a factor similar to 30 higher resolution than Planck polarisation data. This will make B-BOP a unique tool for characterising the statistical properties of the magnetised ISM and probing the role of magnetic fields in the formation and evolution of the interstellar web of dusty molecular filaments giving birth to most stars in our Galaxy. B-BOP will also be a powerful instrument for studying the magnetism of nearby galaxies and testing Galactic dynamo models, constraining the physics of dust grain alignment, informing the problem of the interaction of cosmic rays with molecular clouds, tracing magnetic fields in the inner layers of protoplanetary disks, and monitoring accretion bursts in embedded protostars.
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| 3. |
- Ritacco, A., et al.
(författare)
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NIKA 150 GHz polarization observations of the Crab nebula and its spectral energy distribution
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 616
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Tidskriftsartikel (refereegranskat)abstract
- The Crab nebula is a supernova remnant exhibiting a highly polarized synchrotron radiation at radio and millimetre wavelengths. It is the brightest source in the microwave sky with an extension of 7 by 5 arcmin, and is commonly used as a standard candle for any experiment which aims to measure the polarization of the sky. Though its spectral energy distribution has been well characterized in total intensity, polarization data are still lacking at millimetre wavelengths. We report in this paper high resolution observations (18 00 FWHM) of the Crab nebula in total intensity and linear polarization at 150 GHz with the NIKA camera. NIKA, operated at the IRAM 30 m telescope from 2012 to 2015, is a camera made of Lumped Element Kinetic Inductance Detectors (LEKIDs) observing the sky at 150 and 260 GHz. From these observations we are able to reconstruct the spatial distribution of the polarization degree and angle of the Crab nebula, which is found to be compatible with previous observations at lower and higher frequencies. Averaging across the source and using other existing data sets we find that the Crab nebula polarization angle is consistent with being constant over a wide range of frequencies with a value of -87.7 degrees +/- 0.3 in Galactic coordinates. We also present the first estimation of the Crab nebula spectral energy distribution polarized flux in a wide frequency range: 30-353 GHz. Assuming a single power law emission model we find that the polarization spectral index beta(pol) = -0.347 +/- 0.026 is compatible with the intensity spectral index beta = -0.323 +/- 0.001.
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| 4. |
- Adam, R. M., et al.
(författare)
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The XXL Survey: LI. Pressure profile and Y SZ -M scaling relation in three low-mass galaxy clusters at z∼1 observed with NIKA2
- 2024
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 684
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Tidskriftsartikel (refereegranskat)abstract
- Context. The thermodynamical properties of the intracluster medium (ICM) are driven by scale-free gravitational collapse, but they also reflect the rich astrophysical processes at play in galaxy clusters. At low masses (∼1014M) and high redshift (z≳1), these properties remain poorly constrained, observationally speaking, due to the difficulty in obtaining resolved and sensitive data. Aims. We aim to investigate the inner structure of the ICM as seen through the Sunyaev-Zel’dovich (SZ) effect in this regime of mass and redshift. We focused on the thermal pressure profile and the scaling relation between SZ flux and mass, namely the YSZ-M scaling relation. Methods. The three galaxy clusters XLSSC 072 (z=1.002), XLSSC 100 (z=0.915), and XLSSC 102 (z=0.969), with M500∼2×1014M, were selected from the XXL X-ray survey and observed with the NIKA2 millimeter camera to image their SZ signal. XMM-Newton X-ray data were used as a complement to the NIKA2 data to derive masses based on the YX-M relation and the hydrostatic equilibrium. Results. The SZ images of the three clusters, along with the X-ray and optical data, indicate dynamical activity related to merging events. The pressure profile is consistent with that expected for morphologically disturbed systems, with a relatively flat core and a shallow outer slope. Despite significant disturbances in the ICM, the three high-redshift low-mass clusters follow the YSZ-M relation expected from standard evolution remarkably well. Conclusions. These results indicate that the dominant physics that drives cluster evolution is already in place by z∼1, at least for systems with masses above M500∼1014M.
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| 5. |
- Borodina, I., et al.
(författare)
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Establishing a synthetic pathway for high-level production of 3-hydroxypropionic acid in Saccharomyces cerevisiae via beta-alanine
- 2015
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Ingår i: Metabolic Engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 27, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Microbial fermentation of renewable feedstocks into plastic monomers can decrease our fossil dependence and reduce global CO2 emissions. 3-Hydroxypropionic acid (3HP) is a potential chemical building block for sustainable production of superabsorbent polymers and acrylic plastics. With the objective of developing Saccharolnyces cerevisiae as an efficient cell factory for high-level production of 3HP, we identified the beta-alanine biosynthetic route as the most economically attractive according to the metabolic modeling. We engineered and optimized a synthetic pathway for de novo biosynthesis of beta-alanine and its subsequent conversion into 3HP using a novel beta-alanine-pyruvate aminotransferase discovered in Bacillus cereus. The final strain produced 3HP at a titer of 13.7 +/- 0.3 g L-1 with a 0.14 +/- 0.0 C-mol C-mol(-1) yield on glucose in 80 h in controlled fed-batch fermentation in mineral medium at pH 5, and this work therefore lays the basis for developing a process for biological 3HP production.
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| 6. |
- Kildegaard, K. R., et al.
(författare)
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Engineering and systems-level analysis of Saccharomyces cerevisiae for production of 3-hydroxypropionic acid via malonyl-CoA reductase-dependent pathway
- 2016
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Ingår i: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: In the future, oil-and gas-derived polymers may be replaced with bio-based polymers, produced from renewable feedstocks using engineered cell factories. Acrylic acid and acrylic esters with an estimated world annual production of approximately 6 million tons by 2017 can be derived from 3-hydroxypropionic acid (3HP), which can be produced by microbial fermentation. For an economically viable process 3HP must be produced at high titer, rate and yield and preferably at low pH to minimize downstream processing costs. Results: Here we describe the metabolic engineering of baker's yeast Saccharomyces cerevisiae for biosynthesis of 3HP via a malonyl-CoA reductase (MCR)-dependent pathway. Integration of multiple copies of MCR from Chloroflexus aurantiacus and of phosphorylation-deficient acetyl-CoA carboxylase ACC1 genes into the genome of yeast increased 3HP titer fivefold in comparison with single integration. Furthermore we optimized the supply of acetyl-CoA by overexpressing native pyruvate decarboxylase PDC1, aldehyde dehydrogenase ALD6, and acetyl-CoA synthase from Salmonella enterica SEacsL641P. Finally we engineered the cofactor specificity of the glyceraldehyde-3-phosphate dehydrogenase to increase the intracellular production of NADPH at the expense of NADH and thus improve 3HP production and reduce formation of glycerol as by-product. The final strain produced 9.8 +/- 0.4 g L-1 3HP with a yield of 13 % C-mol C-mol(-1) glucose after 100 h in carbon-limited fed-batch cultivation at pH 5. The 3HP-producing strain was characterized by C-13 metabolic flux analysis and by transcriptome analysis, which revealed some unexpected consequences of the undertaken metabolic engineering strategy, and based on this data, future metabolic engineering directions are proposed. Conclusions: In this study, S. cerevisiae was engineered for high-level production of 3HP by increasing the copy numbers of biosynthetic genes and improving flux towards precursors and redox cofactors. This strain represents a good platform for further optimization of 3HP production and hence an important step towards potential commercial bio-based production of 3HP.
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| 7. |
- Maury, J., et al.
(författare)
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EasyCloneMulti: A Set of Vectors for Simultaneous and Multiple Genomic Integrations in Saccharomyces cerevisiae
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203 .- 1932-6203. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Saccharomyces cerevisiae is widely used in the biotechnology industry for production of ethanol, recombinant proteins, food ingredients and other chemicals. In order to generate highly producing and stable strains, genome integration of genes encoding metabolic pathway enzymes is the preferred option. However, integration of pathway genes in single or few copies, especially those encoding rate-controlling steps, is often not sufficient to sustain high metabolic fluxes. By exploiting the sequence diversity in the long terminal repeats (LTR) of Ty retrotransposons, we developed a new set of integrative vectors, EasyCloneMulti, that enables multiple and simultaneous integration of genes in S. cerevisiae. By creating vector backbones that combine consensus sequences that aim at targeting subsets of Ty sequences and a quickly degrading selective marker, integrations at multiple genomic loci and a range of expression levels were obtained, as assessed with the green fluorescent protein (GFP) reporter system. The EasyCloneMulti vector set was applied to balance the expression of the rate-controlling step in the beta-alanine pathway for biosynthesis of 3-hydroxypropionic acid (3HP). The best 3HP producing clone, with 5.45 g.L-1 of 3HP, produced 11 times more 3HP than the lowest producing clone, which demonstrates the capability of EasyCloneMulti vectors to impact metabolic pathway enzyme activity.
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| 8. |
- Böckler, H B, et al.
(författare)
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Metrology infrastructure for high-pressure gas and liquified hydrogen flows. A brief outline of the MetHyInfra project, measurement challenges, and first results
- 2024
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Ingår i: Measurement. - : Elsevier B.V.. - 0263-2241 .- 1873-412X. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- This paper gives an overview of the ongoing Joint Research Project (JRP) 20IND11 “Metrology infrastructure for high pressure gas and liquefied hydrogen flows” (MetHyInfra), which will ensure traceability in the hydrogen distribution chain. For this purpose, very precise nozzles with well-defined geometries have been produced. In this project, Critical Flow Venturi Nozzles (CFVNs) will be traceably calibrated for the first time with hydrogen and pressures up to 100 MPa using a Coriolis Flow Meter (CFM) as a secondary standard. A CFM has been successfully calibrated with hydrogen against a gravimetric primary standard. Equations of State (EoS) are important for the high-pressure calibration of the nozzles, but also for Computational Fluid Dynamics (CFD) simulations. With regard to CFD, a numerical model has been developed to simulate high pressure hydrogen flow in the CFVN. In a parameter study, non-ideal nozzle shapes are investigated using a shape variation parameter. New Speed of Sound (SoS) measurements were conducted at temperatures from 273 to 323 K and pressures from 1 to 100 MPa. These new data were then used to develop a new EoS for normal hydrogen, optimized for gas phase calculations. In addition to gaseous hydrogen, the project has a strong focus on liquefied hydrogen. Here a three-pronged approach allows traceable measurements. Each of the approaches presented is based on a unique flow calibration principle and relies on independent traceability schemes. The results of the project will ensure traceable measurements and thus a higher level of confidence among end users. © 2024 The Authors
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| 9. |
- Jensen, N. B., et al.
(författare)
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EasyClone: method for iterative chromosomal integration of multiple genes in Saccharomyces cerevisiae
- 2014
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 14:2, s. 238-248
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Tidskriftsartikel (refereegranskat)abstract
- Development of strains for efficient production of chemicals and pharmaceuticals requires multiple rounds of genetic engineering. In this study, we describe construction and characterization of EasyClone vector set for baker's yeast Saccharomyces cerevisiae, which enables simultaneous expression of multiple genes with an option of recycling selection markers. The vectors combine the advantage of efficient uracil excision reaction-based cloning and Cre-LoxP-mediated marker recycling system. The episomal and integrative vector sets were tested by inserting genes encoding cyan, yellow, and red fluorescent proteins into separate vectors and analyzing for co-expression of proteins by flow cytometry. Cells expressing genes encoding for the three fluorescent proteins from three integrations exhibited a much higher level of simultaneous expression than cells producing fluorescent proteins encoded on episomal plasmids, where correspondingly 95% and 6% of the cells were within a fluorescence interval of Log(10) mean +/- 15% for all three colors. We demonstrate that selective markers can be simultaneously removed using Cre-mediated recombination and all the integrated heterologous genes remain in the chromosome and show unchanged expression levels. Hence, this system is suitable for metabolic engineering in yeast where multiple rounds of gene introduction and marker recycling can be carried out.
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| 10. |
- Kildegaard, Kanchana R., et al.
(författare)
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Evolution reveals a glutathione-dependent mechanism of 3-hydroxypropionic acid tolerance
- 2014
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Ingår i: Metabolic engineering. - : Elsevier BV. - 1096-7176 .- 1096-7184. ; 26, s. 57-66
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Tidskriftsartikel (refereegranskat)abstract
- Biologically produced 3-hydroxypropionic acid (3HP) is a potential source for sustainable acrylates and can also find direct use as monomer in the production of biodegradable polymers. For industrial scale production there is a need for robust cell factories tolerant to high concentration of 3HP, preferably at low pH. Through adaptive laboratory evolution we selected S. cerevisiae strains with improved tolerance to 3HP at pH 3.5. Genome sequencing followed by functional analysis identified the causal mutation in SFA1 gene encoding S-(hyclroxymerhyl)glutathione dehydrogenase. Based on our findings, we propose that 3HP toxicity is mediated by 3-hydroxypropionic aldehyde (reuterin ) and that glutathione-dependent reactions are used for reuterin detoxification. The identified molecular response to 3HP and reuterin may well be a general mechanism for handling resistance to organic acid and aldehydes by living cells. (C) 2014 International Metabolic Engineering Society Published by Elsevier Inc. On behalf of International Metabolic Engineering Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/)
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