| 1. |
- Rodet, L., et al.
(författare)
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Dynamical masses of M-dwarf binaries in young moving groups I. The case of TWA22 and GJ2060
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 618
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Tidskriftsartikel (refereegranskat)abstract
- Context. Evolutionary models are widely used to infer the mass of stars, brown dwarfs, and giant planets. Their predictions are thought to be less reliable at young ages (<200 Myr) and in the low-mass regime (< 1 M-circle dot). GJ 2060AB and TWA22AB are two rare astrometric M-dwarf binaries, respectively members of the AB Doradus (AB Dor) and Beta Pictoris (beta Pic) moving groups. As their dynamical mass can be measured to within a few years, they can be used to calibrate the evolutionary tracks and set new constraints on the age of young moving groups.Aims. We provide the first dynamical mass measurement of GJ 2060 and a refined measurement of the total mass of TWA22. We also characterize the atmospheric properties of the individual components of GJ 2060 that can be used as inputs to the evolutionary models.Methods. We used NaCo and SPHERE observations at VLT and archival Keck/NIRC2 data to complement the astrometric monitoring of the binaries. We combined the astrometry with new HARPS radial velocities (RVs) and FEROS RVs of GJ 2060. We used a Markov chain MonteCarlo (MCMC) module to estimate posteriors on the orbital parameters and dynamical masses of GJ 2060AB and TWA22AB from the astrometry and RVs. Complementary data obtained with the integral field spectrograph VLT /SINFONI were gathered to extract the individual near-infrared (1.1-2.5 mu m) medium-resolution (R similar to 1500 2000) spectra of GJ 2060A and B. We compared the spectra to those of known objects and to grids of BT-SETTL model spectra to infer the spectral type, bolometric luminosities, and temperatures of those objects.Results. We find a total mass of 0 : 18 +/- 0 : 02 M-circle dot for TWA22, which is in good agreement with model predictions at the age of the fi Pic moving group. We obtain a total mass of 1 : 09 +/- 0 : 10 M-circle dot for GJ 2060. We estimate a spectral type of M1 +/- 0.5, L/L-circle dot = -1.20 +/- 0.05 dex, and T-eff = 3700 +/- 100 K for GJ 2060 A. The B component is a M3 +/- 0 : 5 dwarf with L/L-circle dot = 1.63 +/- 0.05 dex and T-eff = 3400 +/- 100 K. The dynamical mass of GJ 2060AB is inconsistent with the most recent models predictions (BCAH15, PARSEC) for an AB Dor age in the range 50-150 Myr. It is 10%-20% (1-2 sigma, depending on the assumed age) above the model's predictions, corresponding to an underestimation of 0.10-0.20 M fi. Coevality suggests a young age for the system (similar to 50 Myr) according to most evolutionary models.Conclusions. TWA22 validates the predictions of recent evolutionary tracks at similar to 20 Myr. On the other hand, we evidence a 1-2 sigma mismatch between the predicted and observed mass of GJ 2060 AB. This slight departure may indicate that one of the stars hosts a tight companion. Alternatively, this would confirm the model's tendency to underestimate the mass of young low-mass stars.
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| 3. |
- Walther, G, et al.
(författare)
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Report on challenges for SCIs
- 2021
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report discusses the challenges posed by four types of threats – terrorist attacks, cyber-attacks, extreme weather and social unrest – on the following eight smart critical infrastructure systems:a.ALPHA - Finance (financial system): The analysis focuses on disturbed information flow and disabling/manipulating IT and communication systems, including attacks on the “physical layer” using the example of IEMI/HPEM threats, as well as the software layer.b. BRAVO - Energy supply (system): The analysis focuses on disruption of “smart” energy supply in a “smart city”, caused by natural hazards, in this case flooding, leading to cascading effects and severe consequences for other energy-depending SCIs.c. CHARLIE - Health care (system):Focus of the analysis is on all threats that might cause large increases in the numbers of injuries or sick patients within a densely populated area. This will include indirect impacts, e.g. large numbers of injuries caused by a disaster or terrorist attacks or disease epidemics, but also direct impacts, e.g. service disruptions in critical health infrastructures, such as hospitals, due to attacks or disasters hitting the infrastructure itself.d.DELTA - Transportation (system) – airports: According to the framework situation, threats on Smart Airports will be assessed under circumstances of (i) blocked traffic, (ii) passenger and airplane traffic exceeding capacity (iii) flood.e. ECHO - Industry (in zones in cities) "Industrial Production Plants":The analysis focuses mainly on technological accidents within the refinery complex, but also accidents caused by natural hazards affecting refinery property outside the main refinery complex, e.g. accident on jetty belonging to refinery on the river Danube during unloading/loading oil products from barge to a tank, damages by a gale or storm on process installations (pipes, hoses) resulting in river pollution. Both scenarios could lead to cascading effects for other SCIs in close vicinity.f. FOXTROT - Water supply (systems): The analysis focuses on three cases of local and regional drinking water supply chains, with different kinds of vulnerabilities in terms of climate threats, ICT challenges, security issues and human error.g.GOLF - Urban flood protection (systems): The analysis focuses in the disruption of water and transport caused through tidal and fluvial flooding events.h. HOTEL: City of Helsinki - Flooding underground coal storage. Resilience of the energy infrastructure (city environment).The way this analysis was conducted was by assessing these threats using a 5x5 framework matrix. The two axes of the matrix were phases (understand risks, anticipate/prepare, absorb/withstand, respond/recover, adapt/learn) and dimensions (system/physical, information/data, organizational/business, societal/political, cognitive/decision-making).Each individual matrix block was discussed by subject experts who identified specific challenges and implications for each matrix element and rated its relevance (high, medium, low).In terms of the results, the system/physical dimension received the highest number of important challenges.Overall, the most important singular element was to understand risks in the organizational/business dimension. The least importance was attributed to the adapt/learn phase.
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| 4. |
- Andaloussi, Mounir, et al.
(författare)
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Design, Synthesis, and X-ray Crystallographic Studies of alpha-Aryl Substituted Fosmidomycin Analogues as Inhibitors of Mycobacterium tuberculosis 1-Deoxy-D-xylulose 5-Phosphate Reductoisomerase
- 2011
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 54:14, s. 4964-4976
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Tidskriftsartikel (refereegranskat)abstract
- The natural antibiotic fosmidomycin acts via inhibition of 1-deoxy-D-xylulose 5-phosphate reductoisomerase (DXR), an essential enzyme in the non-mevalonate pathway of isoprenoid biosynthesis. Fosmidomycin is active on Mycobacterium tuberculosis DXR (MtDXR), but it lacks antibacterial activity probably because of poor uptake. alpha-Aryl substituted fosmidomycin analogues have more favorable physicochemical properties and are also more active in inhibiting malaria parasite growth. We have solved crystal structures of MtDXR in complex with 3,4-dichlorophenyl substituted fosmidomycin analogues; these show important differences compared to our previously described forsmidomycin-DXR complex. Our best inhibitor has an IC(50) = 0.15 mu M on MtDXR but still lacked activity in a mycobacterial growth assay (MIC > 32 mu g/mL). The combined results, however, provide insights into how DXR accommodates the new inhibitors and serve as an excellent starting point for the design of other novel and more potent inhibitors, particularly against pathogens where uptake is less of a problem, such as the malaria parasite.
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| 6. |
- Bergfors, C., et al.
(författare)
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Characterization of close visual binaries from the AstraLux Large M Dwarf Survey
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 456:3, s. 2576-2585
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Tidskriftsartikel (refereegranskat)abstract
- We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI) J, H + K spectra of seven close visual pairs in M dwarf binary/triple systems, discovered or observed by the AstraLux M dwarf survey. We determine the spectral types to within +/- 1.0 subclasses from comparison to template spectra and the strength of K-band water absorption, and derive effective temperatures. The results are compared to optical spectral types of the unresolved binary/multiple systems, and we confirm that our photometric method to derive spectral types in the AstraLux M dwarf survey is accurate. We look for signs of youth such as chromospheric activity and low surface gravity, and find an age in the range 0.25-1 Gyr for the GJ 852 system. Strong Li absorption is detected in optical spectra of the triple system J024902 obtained with the Fiberfed Extended Range Optical Spectrograph (FEROS) at the European Southern Observatory (ESO)-Max-Planck-Gesellschaft (MPG) 2.2 m telescope. The equivalent width of the absorption suggests an age consistent with the beta Pic moving group. However, further observations are needed to establish group membership. Ongoing orbital monitoring will provide dynamical masses and thus calibration of evolutionary models for low mass stars.
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| 7. |
- Bergfors, M, et al.
(författare)
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Short-term effects of repetitive arm work and dynamic exercise on glucose metabolism and insulin sensitivity.
- 2005
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 183:4, s. 345-356
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To detennine whether repetitive ann work, with a large component of static muscle contraction alters glucose metabolism and insulin sensitivity. Methad: Euglycemic clamps (2h) were started in ten healthy individuals 15 minutes after 37 minute periods of: 1) repetitive ann work in a simulated occupational setting; 2) dynamic concentric exercise on a cycle ergometer at 60% OfVO2 max and 3) a resting regime as a control. During the experimental periods, blood samples were collected, blood pressure was measured repeatedly and electrocardiogram (ECG) wasrecorded continuously. During the clamps, euglycemia was maintained at 5 mmo1/l and insulin was infused at 56 mU/m2/min for 120 min. Results: The insulin-mediated glucose disposal rate (M-value) for the steady state period (60- 120 min) of the clamp, tended to be lower following ann work than for both cycling and resting regimes. When dividing the steady state period into 20-minute intervals, the insulin sensitivity index, (ISI) was significantly lower for ann work compared with the resting control situation between 60-80 minutes (p=0.04) and 80-100 minutes (p=0.01) respectively. Catecholamines increased significantly for ann work and cycling compared with resting regime. .Data from heart rate variability (HRV) me asurements indicated significant sympathetic activation during repetitive ann work test. Canelusian: The results indicate that repetitive ann work might acutely promote insulin resistance, whereas no such effect on insulin resistance was produced by dynamic concentric exercise.
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| 8. |
- Björkelid, Christofer, et al.
(författare)
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Structural and functional studies of mycobacterial IspD enzymes
- 2011
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Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 67, s. 403-414
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Tidskriftsartikel (refereegranskat)abstract
- A number of pathogens, including the causative agents of tuberculosis and malaria, synthesize isopentenyl diphosphate via the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway rather than the classical mevalonate pathway found in humans. As part of a structure-based drug-discovery program against tuberculosis, IspD, the enzyme that carries out the third step in the MEP pathway, was targeted. Constructs of both the Mycobacterium smegmatis and the Mycobacterium tuberculosis enzymes that were suitable for structural and inhibitor-screening studies were engineered. Two crystal structures of the M. smegmatis enzyme were produced, one in complex with CTP and the other in complex with CMP. In addition, the M. tuberculosis enzyme was crystallized in complex with CTP. Here, the structure determination and crystallographic refinement of these crystal forms and the enzymatic characterization of the M. tuberculosis enzyme construct are reported. A comparison with known IspD structures allowed the definition of the structurally conserved core of the enzyme. It indicates potential flexibility in the enzyme and in particular in areas close to the active site. These well behaved constructs provide tools for future target-based screening of potential inhibitors. The conserved nature of the extended active site suggests that any new inhibitor will potentially exhibit broad-spectrum activity.
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| 9. |
- Hallberg, B. M., et al.
(författare)
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A new scaffold for binding haem in the cytochrome domain of the extracellular flavocytochrome cellobiose dehydrogenase
- 2000
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Ingår i: Structure. - 0969-2126 .- 1878-4186. ; 8:1, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- Background: The fungal oxidoreductase cellobiose dehydrogenase (CDH) degrades both lignin and cellulose, and is the only known extracellular flavocytochrome. This haemoflavoenzyme has a multidomain organisation with a b-type cytochrome domain linked to a large flavodehydrogenase domain. The two domains can be separated proteolytically to yield a functional cytochrome and a flavodehydrogenase. Here, we report the crystal structure of the cytochrome domain of CDH. Results: The crystal structure of the b-type cytochrome domain of CDH from the wood-degrading fungus Phanerochaete chrysosporium has been determined at 1.9 Angstrom resolution using multiple isomorphous replacement ncluding anomalous scattering information. Three models of the cytochrome have been refined: the in vitro prepared cytochrome in its redox-inactive state (pH 7.5) and redox-active state (pH 4.6), as well as the naturally occurring cytochrome fragment. Conclusions: The 190-residue long cytochrome domain of CDH folds as a beta sandwich with the topology of the antibody Fab V-H domain. The haem iron is ligated by Met65 and His 163, which confirms previous results from spectroscopic studies. This is only the second example of a b-type cytochrome with this ligation, the first being cytochrome b(562). The haem-propionate groups are surface exposed and, therefore, might play a role in the association between the cytochrome and flavoprotein domain, and in interdomain electron transfer. There are no large differences in overall structure of the cytochrome at redoxactive pH as compared with the inactive form, which excludes the possibility that pH-dependent redox inactivation results from partial denaturation. From the electron-density map of the naturally occurring cytochrome, we conclude that it corresponds to the proteolytically prepared cytochrome domain.
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| 11. |
- Johansson, P., et al.
(författare)
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Crystallization and preliminary X-ray analysis of a xyloglucan endotransglycosylase from Populus tremula x tremuloides
- 2003
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Ingår i: Acta Crystallographica Section D. - 0907-4449 .- 1399-0047. ; 59, s. 535-537
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Tidskriftsartikel (refereegranskat)abstract
- Xyloglucan endotransglycosylases (XETs) cleave and religate xyloglucan polymers in plant cell walls. Recombinant XET from poplar has been purified from a Pichia pastoris expression system and crystallized. Two different crystal forms were obtained by vapour diffusion from potassium sodium tartrate and from an imidazole buffer using sodium acetate as a precipitant. Data were collected from these crystal forms to 3.5 and 2.1 Angstrom resolution, respectively. The first crystal form was found to belong to space group P3(1)21 or P3(2)21 (unit-cell parameters a = 98.6, b = 98.6, c = 98.5 Angstrom) and the second crystal form to space group P6(3) (unit-cell parameters a = 188.7, b = 188.7, c = 46.1 Angstrom).
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