| 1. |
- de Graauw, Th., et al.
(författare)
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The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI)
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L6-
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Tidskriftsartikel (refereegranskat)abstract
- Aims: This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods: The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results: After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
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| 2. |
- Bossard, G., et al.
(författare)
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Integral invariants in maximally supersymmetric Yang-Mills theories
- 2011
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Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :5, s. 021-
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Tidskriftsartikel (refereegranskat)abstract
- Integral invariants in maximally supersymmetric Yang-Mills theories are discussed in spacetime dimensions 4 <= D <= 10 for SU(k) gauge groups. It is shown that, in addition to the action, there are three special invariants in all dimensions. Two of these, the single-and double-trace F-4 invariants, are of Chern-Simons type in D = 9, 10 and BPS type in D <= 8, while the third, the double-trace of two derivatives acting on F-4, can be expressed in terms of a gauge-invariant super-D-form in all dimensions. We show that the super-ten-forms for D = 10 F-4 invariants have interesting cohomological properties and we also discuss some features of other invariants, including the single-trace d(2)F(4), which has a special form in D = 10. The implications of these results for ultra-violet divergences are discussed in the framework of algebraic renormalisation.
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| 3. |
- Henriksen, Kim, et al.
(författare)
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Dissociation of Bone Resorption and Bone Formation in Adult Mice with a Non-Functional V-ATPase in Osteoclasts Leads to Increased Bone Strength
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:11
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Tidskriftsartikel (refereegranskat)abstract
- Osteopetrosis caused by defective acid secretion by the osteoclast, is characterized by defective bone resorption, increased osteoclast numbers, while bone formation is normal or increased. In contrast the bones are of poor quality, despite this uncoupling of formation from resorption. To shed light on the effect of uncoupling in adult mice with respect to bone strength, we transplanted irradiated three-month old normal mice with hematopoietic stem cells from control or oc/oc mice, which have defective acid secretion, and followed them for 12 to 28 weeks. Engraftment levels were assessed by flow cytometry of peripheral blood. Serum samples were collected every six weeks for measurement of bone turnover markers. At termination bones were collected for mu CT and mechanical testing. An engraftment level of 98% was obtained. From week 6 until termination bone resorption was significantly reduced, while the osteoclast number was increased when comparing oc/oc to controls. Bone formation was elevated at week 6, normalized at week 12, and reduced onwards. mu CT and mechanical analyses of femurs and vertebrae showed increased bone volume and bone strength of cortical and trabecular bone. In conclusion, these data show that attenuation of acid secretion in adult mice leads to uncoupling and improves bone strength.
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| 4. |
- Malmerberg, Erik, 1980, et al.
(författare)
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Time-Resolved WAXS Reveals Accelerated Conformational Changes in Iodoretinal-Substituted Proteorhodopsin.
- 2011
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Ingår i: Biophysical journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 101:6, s. 1345-53
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Tidskriftsartikel (refereegranskat)abstract
- Time-resolved wide-angle x-ray scattering (TR-WAXS) is an emerging biophysical method which probes protein conformational changes with time. Here we present a comparative TR-WAXS study of native green-absorbing proteorhodopsin (pR) from SAR86 and a halogenated derivative for which the retinal chromophore has been replaced with 13-desmethyl-13-iodoretinal (13-I-pR). Transient absorption spectroscopy differences show that the 13-I-pR photocycle is both accelerated and displays more complex kinetics than native pR. TR-WAXS difference data also reveal that protein structural changes rise and decay an order-of-magnitude more rapidly for 13-I-pR than native pR. Despite these differences, the amplitude andnature of the observed helical motions are not significantly affected by the substitution of the retinal's C-20 methyl group with an iodine atom. Molecular dynamics simulations indicate that a significant increase in free energy is associated with the 13-cis conformation of 13-I-pR, consistent with our observation that the transient 13-I-pR conformational state is reached more rapidly. We conclude that although the conformational trajectory is accelerated, the major transient conformation of pR is unaffected by the substitution of an iodinated retinal chromophore.
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| 5. |
- Nüske, Ralf, et al.
(författare)
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Picosecond time-resolved x-ray refectivity of a laser-heated amorphous carbon film
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:10
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate thin film x-ray reflectivity measurements with picosecond time resolution. Amorphous carbon films with a thickness of 46 nm were excited with laser pulses characterized by 100 fs duration, a wavelength of 800 nm, and a fluence of 70 mJ/cm(2). The laser-induced stress caused a rapid expansion of the thin film followed by a relaxation of the film thickness as heat diffused into the silicon substrate. We were able to measure changes in film thickness as small as 0.2 nm. The relaxation dynamics are consistent with a model which accounts for carrier-enhanced substrate heat diffusivity. (C) 2011 American Institute of Physics. [doi:10.1063/1.3562967]
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| 6. |
- Steinhoff, Franciska S., et al.
(författare)
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Cyanobacteria in Scandinavian coastal waters - A potential source for biofuels and fatty acids?
- 2014
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Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 5, s. 42-51
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Tidskriftsartikel (refereegranskat)abstract
- Since land-based biofuel production competes with conventional food production, a water-based biomass and biofuel production from cyanobacteria offers large potential. This study investigates the application potential of cyanobacteria for fuel production and by-products by mimicking nutrient depleted environmental conditions. Three Baltic cyanobacteria strains (Aphanizomenon flos-aquae, Dolichospermum lemmermannii and Nodularia spumigena) were inoculated in full nutrient levels, as well as phosphorus and nitrogen depleted medium, before being monitored for 14 days. For screening reasons, multiple parameters such as fatty acids, photosynthetic pigments including phycobilins, biovolume, photosynthetic activity, inorganic nutrients, particulate organic carbon, nitrogen and phosphorous were investigated every seven days. We observed a strong negative relationship between lipid content, growth and nutrient availability, resulting in high lipid and pigment production in combination with a limited growth rate in nutrient depleted treatments. Our results suggest that cultivation and harvest of bloom-forming cyanobacteria for fuel and by-product production are feasible in Scandinavia, but strongly depends on the desired compounds and biomass. Each cyanobacteria species originally has a species-specific chemical fingerprint that may be modified by rearing conditions and harvesting period to meet the needs of the consumer. This leads to important conclusions regarding future culturing conditions and biomass production of the desired compounds.
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| 7. |
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