| 1. |
- Both, C., et al.
(författare)
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Large-scale geographical variation confirms that climate change causes birds to lay earlier
- 2004
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Ingår i: Proceedings of the Royal Society of London Series B-Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 271:1549, s. 1657-1662
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Tidskriftsartikel (refereegranskat)abstract
- Advances in the phenology of organisms are often attributed to climate change, but alternatively, may reflect a publication bias towards advances and may be caused by environmental factors unrelated to climate change. Both factors are investigated using the breeding dates of 25 long-term studied populations of Ficedula flycatchers across Europe. Trends in spring temperature varied markedly between study sites, and across populations the advancement of laying date was stronger in areas where the spring temperatures increased more, giving support to the theory that climate change causally affects breeding date advancement.
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| 2. |
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| 3. |
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| 4. |
- Piersma, T, et al.
(författare)
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High daily energy expenditure of incubating shorebirds on High Arctic tundra: a circumpolar study
- 2003
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Ingår i: Functional Ecology. - : Wiley. - 1365-2435 .- 0269-8463. ; 17:3, s. 356-362
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Tidskriftsartikel (refereegranskat)abstract
- 1. Given the allometric scaling of thermoregulatory capacity in birds, and the cold and exposed Arctic environment, it was predicted that Arctic-breeding shorebirds should incur high costs during incubation. Using doubly labelled water (DLW), daily energy expenditure (DEE) during incubation was measured in eight shorebird species weighing between 29 and 142 g at various sites in the Eurasian and Canadian High Arctic. The results are compared with a compilation of similar data for birds at lower latitudes. 2. There was a significant positive correlation between species average DEE and body mass (DEE (kJ day(-1) )=28.12 BM (g)(0.524) , r(2)=0.90). The slopes of the allometric regression lines for DEE on body mass of tundra-breeding birds and lower latitude species (a sample mostly of passerines but including several shorebirds) are similar (0.548 vs 0.545). DEE is about 50% higher in birds on the tundra than in temperate breeding areas. 3. Data for radiomarked Red Knots for which the time budgets during DLW measurements were known, indicated that foraging away from the nest on open tundra is almost twice as costly as incubating a four-egg clutch. 4. During the incubation phase in the High Arctic, tundra-breeding shorebirds appear to incur among the highest DEE levels of any time of the year. The rates of energy expenditure measured here are among the highest reported in the literature so far, reaching inferred ceilings of sustainable energy turnover rates.
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| 5. |
- Ademark, Pia, et al.
(författare)
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Cloning and characterisation of Aspergillus niger genes encoding an alpha-galactosidase and a beta-mannosidase involved in galactomannan degradation
- 2001
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956. ; 268:10, s. 2982-2990
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Tidskriftsartikel (refereegranskat)abstract
- α-Galactosidase (EC 3.2.1.22) and β-mannosidase (EC 3.2.1.25) participate in the hydrolysis of complex plant saccharides such as galacto(gluco)mannans. Here we report on the cloning and characterization of genes encoding an α-galactosidase (AglC) and a β-mannosidase (MndA) from Aspergillus niger. The aglC and mndA genes code for 747 and 931 amino acids, respectively, including the eukaryotic signal sequences. The predicted isoelectric points of AglC and MndA are 4.56 and 5.17, and the calculated molecular masses are 79.674 and 102.335 kDa, respectively. Both AglC and MndA contain several putative N-glycosylation sites. AglC was assigned to family 36 of the glycosyl hydrolases and MndA was assigned to family 2. The expression patterns of aglC and mndA and two other genes encoding A. nigerα-galactosidases (aglA and aglB) during cultivation on galactomannan were studied by Northern analysis. A comparison of gene expression on monosaccharides in the A. niger wild-type and a CreA mutant strain showed that the carbon catabolite repressor protein CreA has a strong influence on aglA, but not on aglB, aglC or mndA. AglC and MndA were purified from constructed overexpression strains of A. niger, and the combined action of these enzymes degraded a galactomanno-oligosaccharide into galactose and mannose. The possible roles of AglC and MndA in galactomannan hydrolysis is discussed.
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| 6. |
- Bergmann, U, et al.
(författare)
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High-resolution X-ray spectroscopy of rare events : a different look at local structure and chemistry
- 2001
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Ingår i: Journal of Synchrotron Radiation. - Univ Calif Berkeley, Lawrence Berkeley Lab, Phys Biosci Div, Berkeley, CA 94720 USA. Univ Calif Davis, Dept Appl Sci, Davis, CA 95616 USA. CALTECH, Jet Prop Lab, Pasadena, CA 91109 USA. : MUNKSGAARD INT PUBL LTD. - 0909-0495 .- 1600-5775. ; 8, s. 199-203
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Tidskriftsartikel (refereegranskat)abstract
- The combination of large-acceptance high-resolution X-ray optics with bright synchrotron sources permits quantitative analysis of rare events such as X-ray fluorescence from very dilute systems, weak fluorescence transitions or X-ray Raman scattering. Transition-metal K beta fluorescence contains information about spin and oxidation state; examples of the characterization of the Mn oxidation states in the oxygen-evolving complex of photosystem II and Mn-consuming spores from the marine bacillus SG-1 are presented. Weaker features of the K beta spectrum resulting from valence-level and 'interatomic' ligand to metal transitions contain detailed information on the ligand-atom type, distance and orientation. Applications of this spectral region to characterize the local structure of model compounds are presented. X-ray Raman scattering (XRS) is an extremely rare event, but also represents a unique technique to obtain bulk-sensitive low-energy (<600 eV) X-ray absorption fine structure (XAFS) spectra using hard ( 10 keV) X-rays. A photon is inelastically scattered, losing part of its energy to promote an electron into an unoccupied level. In many cases, the cross section is proportional to that of the corresponding absorption process yielding the same X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) features. XRS finds application for systems that defy XAFS analysis at low energies, e.g. liquids or highly concentrated complex systems, reactive compounds and samples under extreme conditions (pressure, temperature). Recent results are discussed.
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| 8. |
- Friesema, ECH, et al.
(författare)
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Association between mutations in a thyroid hormone transporter and severe X-linked psychomotor retardation
- 2004
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Ingår i: The Lancet. - 1474-547X. ; 364:9443, s. 1435-1437
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Tidskriftsartikel (refereegranskat)abstract
- Monocarboxylate transporter 8 (MCT8) is a thyroid hormone transporter, the gene of which is located on the X chromosome. We tested whether mutations in MCT8 cause severe psychomotor retardation and high serum triiodothyronine (T,) concentrations in five unrelated young boys. The coding sequence of MCT8 was analysed by PCR and direct sequencing of its six exons. In two patients, gene deletions of 2.4 kb and 24 kb were recorded and in three patients missense mutations Ala150Va1, Arg171stop, and Leu397Pro were identified. We suggest that this novel syndrome of X-linked psychomotor retardation is due to a defect in T-3 entry into neurons through MCT8, resulting in impaired T-3 action and metabolism.
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| 9. |
- Groenhof, Gerrit, et al.
(författare)
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Photoactivation of the photoactive yellow protein : why photon absorption triggers a trans-to-cis Isomerization of the chromophore in the protein.
- 2004
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126:13, s. 4228-4233
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Tidskriftsartikel (refereegranskat)abstract
- Atomistic QM/MM simulations have been carried out on the complete photocycle of Photoactive Yellow Protein, a bacterial photoreceptor, in which blue light triggers isomerization of a covalently bound chromophore. The "chemical role" of the protein cavity in the control of the photoisomerization step has been elucidated. Isomerization is facilitated due to preferential electrostatic stabilization of the chromophore's excited state by the guanidium group of Arg52, located just above the negatively charged chromophore ring. In vacuo isomerization does not occur. Isomerization of the double bond is enhanced relative to isomerization of a single bond due to the steric interactions between the phenyl ring of the chromophore and the side chains of Arg52 and Phe62. In the isomerized configuration (ground-state cis), a proton transfer from Glu46 to the chromophore is far more probable than in the initial configuration (ground-state trans). It is this proton transfer that initiates the conformational changes within the protein, which are believed to lead to signaling.
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| 10. |
- Messinger, Johannes, 1963-, et al.
(författare)
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Absence of Mn-centered oxidation in the S2 → S3 Transition: : Implications for the mechanism of photosynthetic water oxidation
- 2001
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 123:32, s. 7804-7820
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Tidskriftsartikel (refereegranskat)abstract
- A key question for the understanding of photosynthetic water oxidation is whether the four oxidizing equivalents necessary to oxidize water to dioxygen are accumulated on the four Mn ions of the oxygen-evolving complex (OEC), or whether some ligand-centered oxidations take place before the formation and release of dioxygen during the S-3 --> [S-4] --> So transition. Progress in instrumentation and flash sample preparation allowed us to apply Mn K beta X-ray emission spectroscopy (K beta XES) to this problem for the first time. The K beta XES results, in combination with Mn X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) data obtained from the same set of samples, show that the S-2 --> S3 transition, in contrast to the S-0 --> S-1 and S-1 --> S-2 transitions. does not involve a Mn-centered oxidation. On the basis of new structural data from the S-3-state, manganese mu -oxo bridge radical formation is proposed for the S-2 --> S-3 transition, and three possible mechanisms for the O-O bond formation are presented.
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| 11. |
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| 12. |
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| 13. |
- Winblad, B, et al.
(författare)
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Mild cognitive impairment--beyond controversies, towards a consensus: report of the International Working Group on Mild Cognitive Impairment.
- 2004
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Ingår i: Journal of internal medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 256:3, s. 240-6
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Forskningsöversikt (refereegranskat)abstract
- The First Key Symposium was held in Stockholm, Sweden, 2-5 September 2003. The aim of the symposium was to integrate clinical and epidemiological perspectives on the topic of Mild Cognitive Impairment (MCI). A multidisciplinary, international group of experts discussed the current status and future directions of MCI, with regard to clinical presentation, cognitive and functional assessment, and the role of neuroimaging, biomarkers and genetics. Agreement on new perspectives, as well as recommendations for management and future research were discussed by the international working group. The specific recommendations for the general MCI criteria include the following: (i) the person is neither normal nor demented; (ii) there is evidence of cognitive deterioration shown by either objectively measured decline over time and/or subjective report of decline by self and/or informant in conjunction with objective cognitive deficits; and (iii) activities of daily living are preserved and complex instrumental functions are either intact or minimally impaired.
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| 14. |
- Wingbrant, Helena, et al.
(författare)
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MISiCFET chemical sensors for applications in exhaust gases and flue gases
- 2002
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Ingår i: Materials Science Forum. - 0255-5476 .- 1662-9752. ; 433-4, s. 953-956
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Tidskriftsartikel (refereegranskat)abstract
- A chemical gas sensor based on a silicon carbide field effect transistor with a catalytic gate metal has been under development for a number of years. The choice of silicon carbide as the semiconductor material allows the sensor to operate at high temperatures, for more than 6 months in flue gases at 300degreesC and for at least three days at 700degreesC. The chemical inertness of silicon carbide and a buried gate design makes it a suitable sensor technology for applications in corrosive environments such as exhaust gases and flue gases from boilers. The selectivity of the sensor devices is established through the choice of type and structure of the gate metal as well as the operation temperature. In this way NH3 sensors with low cross sensitivity to NOx have been demonstrated as potential sensors for control of selective catalytic reduction (SCR) of NOx by urea injection into diesel exhausts. Here we show that sensors with a porous platinum or iridium gate show different temperature ranges for NH3 detection. The hardness of the silicon carbide makes it for example more resistant to water splash at cold start of a petrol engine than existing technologies, and a sensor which can control the air to fuel ratio, before the exhaust gases are heated, has been demonstrated. Silicon carbide sensors are also tested in flue gases from boilers. Efficient regulation of the combustion in a boiler will decrease fuel consumption and reduce emissions.
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