| 1. |
- Meyer, H., et al.
(författare)
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Overview of physics results from MAST
- 2009
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 49:10, s. 104017-
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Tidskriftsartikel (refereegranskat)abstract
- Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks (STs). Using the increased heating capabilities P-NBI <= 3.8 MW H-mode at I-P = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with I-P and more strongly with B-t than in the ITER IPB98(y, 2) scaling. Measurements of the fuel retention of shallow pellets extrapolate to an ITER particle throughput of 70% of its original designed total throughput capacity. The anomalous momentum diffusion, chi(phi), is linked to the ion diffusion, chi(i), with a Prandtl number close to P-phi approximate to chi(phi)/chi(i) approximate to 1, although chi(i) approaches neoclassical values. New high spatial resolution measurements of the edge radial electric field, E-r, show that the position of steepest gradients in electron pressure and E-r (i.e. shearing rate) are coincident, but their magnitudes are not linked. The T-e pedestal width on MAST scales with root beta(ped)(pol) rather than rho(pol). The edge localized mode (ELM) frequency for type-IV ELMs, new in MAST, was almost doubled using n = 2 resonant magnetic perturbations from a set of four external coils (n = 1, 2). A new internal 12 coil set (n <= 3) has been commissioned. The filaments in the inter-ELM and L-mode phase are different from ELM filaments, and the characteristics in L-mode agree well with turbulence calculations. A variety of fast particle driven instabilities were studied from 10 kHz saturated fishbone like activity up to 3.8 MHz compressional Alfven eigenmodes. Fast particle instabilities also affect the off-axis NBI current drive, leading to fast ion diffusion of the order of 0.5 m(2) s(-1) and a reduction in the driven current fraction from 40% to 30%. EBW current drive start-up is demonstrated for the first time in a ST generating plasma currents up to 55 kA. Many of these studies contributed to the physics basis of a planned upgrade to MAST.
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| 2. |
- Lloyd, B., et al.
(författare)
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Overview of physics results from MAST
- 2007
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Ingår i: Nuclear Fusion. - 0029-5515 .- 1741-4326. ; 47:10, s. S658-S667
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Tidskriftsartikel (refereegranskat)abstract
- Substantial advances have been made on the Mega AmpÚre Spherical Tokamak (MAST). The parameter range of the MAST confinement database has been extended and it now also includes pellet-fuelled discharges. Good pellet retention has been observed in H-mode discharges without triggering an ELM or an H/L transition during peripheral ablation of low speed pellets. Co-ordinated studies on MAST and DIII-D demonstrate a strong link between the aspect ratio and the beta scaling of H-mode energy confinement, consistent with that obtained when MAST data were merged with a subset of the ITPA database. Electron and ion ITBs are readily formed and their evolution has been investigated. Electron and ion thermal diffusivities have been reduced to values close to the ion neoclassical level. Error field correction coils have been used to determine the locked mode threshold scaling which is comparable to that in conventional aspect ratio tokamaks. The impact of plasma rotation on sawteeth has been investigated and the results have been well-modelled using the MISHKA-F code. Alfvén cascades have been observed in discharges with reversed magnetic shear. Measurements during off-axis NBCD and heating are consistent with classical fast ion modelling and indicate efficient heating and significant driven current. Central electron Bernstein wave heating has been observed via the O-X-B mode conversion process in special magnetically compressed plasmas. Plasmas with low pedestal collisionality have been established and further insight has been gained into the characteristics of filamentary structures at the plasma edge. Complex behaviour of the divertor power loading during plasma disruptions has been revealed by high resolution infra-red measurements.
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| 3. |
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| 4. |
- Ardsby, Malin, et al.
(författare)
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Emergency unit capacity in Northern Tanzania: a cross-sectional survey
- 2023
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Ingår i: BMJ Open. - : BMJ PUBLISHING GROUP. - 2044-6055. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionEmergency medicine (EM) is a growing field in Sub-Saharan Africa. Characterising the current capacity of hospitals to provide emergency care is important in identifying gaps and future directions of growth. This study aimed to characterise the ability of emergency units (EU) to provide emergency care in the Kilimanjaro region in Northern Tanzania.MethodsThis was a cross-sectional study conducted at 11 hospitals with emergency care capacity in three districts in the Kilimanjaro region of Northern Tanzania assessed in May 2021. An exhaustive sampling approach was used, whereby all hospitals within the three-district area were surveyed. Hospital representatives were surveyed by two EM physicians using the Hospital Emergency Assessment tool developed by the WHO; data were analysed in Excel and STATA.ResultsAll hospitals provided emergency services 24 hours a day. Nine had a designated area for emergency care, four had a core of fixed providers assigned to the EU, two lacked a protocol for systematic triage. For Airway and Breathing interventions, oxygen administration was adequate in 10 hospitals, yet manual airway manoeuvres were only adequate in six and needle decompression in two. For Circulation interventions, fluid administration was adequate in all facilities, yet intraosseous access and external defibrillation were each only available in two. Only one facility had an ECG readily available in the EU and none was able to administer thrombolytic therapy. For trauma interventions, all facilities could immobilise fractures, yet lacked interventions such as cervical spinal immobilisation and pelvic binding. These deficiencies were primarily due to lack of training and resources.ConclusionMost facilities perform systematic triage of emergency patients, though major gaps were found in the diagnosis and treatment of acute coronary syndrome and initial stabilisation manoeuvres of patients with trauma. Resource limitations were primarily due to equipment and training deficiencies. We recommend the development of future interventions in all levels of facilities to improve the level of training.
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| 5. |
- Guanter, Luis, et al.
(författare)
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Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence
- 2014
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 111:14, s. E1327-E1333
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Tidskriftsartikel (refereegranskat)abstract
- Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas. Recent advances in spectroscopy enable the space-based monitoring of sun-induced chlorophyll fluorescence (SIF) from terrestrial plants. Here we demonstrate that spaceborne SIF retrievals provide a direct measure of the GPP of cropland and grassland ecosystems. Such a strong link with crop photosynthesis is not evident for traditional remotely sensed vegetation indices, nor for more complex carbon cycle models. We use SIF observations to provide a global perspective on agricultural productivity. Our SIF-based crop GPP estimates are 50-75% higher than results from state-of-the-art carbon cycle models over, for example, the US Corn Belt and the Indo-Gangetic Plain, implying that current models severely underestimate the role of management. Our results indicate that SIF data can help us improve our global models for more accurate projections of agricultural productivity and climate impact on crop yields. Extension of our approach to other ecosystems, along with increased observational capabilities for SIF in the near future, holds the prospect of reducing uncertainties in the modeling of the current and future carbon cycle.
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| 6. |
- Hahn Berg, IC, et al.
(författare)
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Salivary protein adsorption onto hydroxyapatite and SDS-mediated elution studied by in situ ellipsometry
- 2001
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Ingår i: Biofouling (Print). - 0892-7014 .- 1029-2454. ; 17, s. 173-187
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Tidskriftsartikel (refereegranskat)abstract
- Whole unstimulated saliva from two donors was investigated both with respect to adsorption characteristics and SDS-induced elutability. Salivary protein adsorption onto hydroxyapatite (HA) discs was studied by means of in situ ellipsometry in the concentration range 0.1-20% saliva. The adsorbed amounts on HA were found to be similar to those on silica, but the rates of adsorption were lower. Protein adsorption was virtually unaffected by the presence of Na+, whereas Ca2+ induced nucleation of calcium phosphate at the surface, the deposition rate being influenced by the pellicle age but not by the presence of saliva in bulk solution. The SDS elutability of adsorbed pellicles was determined on HA as well as on silica surfaces. Desorption from both surfaces was found to occur in the same SDS concentration range, although a residual layer was observed on HA. The slight net positive charge and lower charge density of HA as compared to the strongly negatively charged silica, may, at least partly, account for this observation by causing a reduction in the repulsive force between protein-surfactant complexes and the surface. Interindividual differences, observed in the adsorption as well as elution experiments, are thought to relate to the compositional differences observed by SDS-PAGE
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| 7. |
- Joiner, A, et al.
(författare)
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Adsorption from black tea and red wine onto in vitro salivary pellicles studied by ellipsometry
- 2003
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Ingår i: European Journal of Oral Sciences. - : Blackwell Munksgaard. - 0909-8836 .- 1600-0722. ; 111, s. 417-422
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Tidskriftsartikel (refereegranskat)abstract
- The adsorption of black tea and red wine components onto a pellicle-like protein layer formed in vitro by adsorption from whole unstimulated saliva on hydroxyapatite discs were studied by in situ ellipsometry. It was found that components from black tea readily adsorbed to the pellicle. Subsequent exposure to saliva led to further adsorption of salivary components to give an overall increase in the amounts adsorbed. The amounts adsorbed increased still further following a third tea and saliva exposure. Components of red wine gave significantly greater amounts of adsorption to the pellicle than black tea. The adsorption of components of black tea gave a concomitant increase in colour or stain as measured by a reflectance chromameter. In all cases, the black tea- and red wine-modified pellicles were not eluted by either phosphate buffer or sodium dodecyl sulphate (SDS) rinses. Thus, black tea and red wine components have been shown to have a profound effect on in vitro pellicle maturation, causing thickened layers of stained material to build up, which are not readily removed.
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| 8. |
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| 9. |
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| 10. |
- Rojas, A, et al.
(författare)
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Nicotinamide as a repair inhibitor in vivo: studies using single and fractionated X-ray doses in mouse skin and kidneys
- 1996
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Ingår i: Radiation Research. - 0033-7587. ; 145:4, s. 419-431
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Tidskriftsartikel (refereegranskat)abstract
- Inhibitors of adenosine diphosphoribosyl transferase, like nicotinamide, 3-aminobenzamide and other analogues, can inhibit repair of radiation-induced sublethal and/or potentially lethal damage in some in vitro systems. Therefore, we have tested the effect of nicotinamide on repair parameters in vivo in two rodent normal tissues. In skin, the sensitivity to dose fractionation (1, 2, 5 or 10 X-ray fractions in 5 days) was monitored by defining the alpha/beta ratio in the presence or absence of nicotinamide (0.5 mg g-1) in air or carbogen. Pre- and postirradiation sensitization were investigated using an X-ray schedule of 5 fractions/5 days in carbogen alone or combined with nicotinamide given 1 h before, immediately after or 8 h after irradiation. Also, changes in the steepness of the underlying X-ray survival curve for the target skin clonogens, reflected by a change in the alpha/beta ratio, were investigated using the neutron top-up design. Underlying survival curves for oxygen +/- nicotinamide were obtained over the X-ray dose range 2.5 to 25 Gy, by administering single X-ray doses and following these with single top-up doses of d(4)-Be neutrons. Finally, in mouse kidney, recovery half-times (t1/2) were obtained by determining the time-dependent disappearance of X-ray damage using a split-dose design of two 6-Gy fractions separated by an interval which varied from 0 to 48 h and followed by two top-up doses from a neutron beam. No increase in alpha/beta for epidermal damage was seen with nicotinamide alone and, although sensitization was observed when the drug was given 1 h before irradiation, no postirradiation sensitization was detected. In kidney, there was no significant difference in the proportion of total repairable damage or in the half-life of recovery between treatments given with or without nicotinamide. Therefore, no decrease in normal tissue tolerance should be observed with the use of nicotinamide in clinical radiotherapy resulting either from reduced sparing with dose fractionation or from an increase in residual damage when shortening the interfraction interval. Finally, unless repair of radiation damage in normal tissues in vivo differs markedly from that of tumors, it is unlikely that the large sensitization seen in rodent tumors at 1.5 to 2 Gy per fraction, with carbogen and nicotinamide, can be attributed to nicotinamide acting as a repair inhibitor.
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