| 1. |
- Cappellin, C., et al.
(författare)
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Design of a Push-Broom Multi-Beam Radiometer for Future Ocean Observations
- 2015
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Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856
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Konferensbidrag (refereegranskat)abstract
- The design of a push-broom multi-beam radiometer for future ocean observations is described. The radiometer provides a sensitivity one order of magnitude higher than a traditional conical scanning radiometer, and has the big advantage of being fully stationary relative to the satellite platform. Thanks to a dense focal plane array and a dedicated optimization procedure, the instrument can accurately measure in C, X and Ku band and as close as 15 km to the coast line.
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| 2. |
- Cappellin, C., et al.
(författare)
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Feed array breadboard for future passive microwave radiometer antennas
- 2018
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Ingår i: IET Conference Publications. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- The pattern of a 265 mm x 200 mm breadboard made of 35 x-polarized and 32 y-polarized Vivaldi antennas located above a finite ground plane is computed and measured at 6.9 GHz. The breadboard constitutes the feed array illuminating a 5 m conical scan antenna working at 6.9 GHz for next generation microwave radiometers for ocean observation. The analysis is done including mutual coupling between the elements, and in two commercial software, the MoM add-on to GRASP and CST. The breadboard is measured at the Spherical Near-Field Antenna Test Facility at the Technical University of Denmark.
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| 3. |
- Iupikov, Oleg, 1983, et al.
(författare)
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An Optimal Beamforming Algorithm for Phased-Array Antennas Used in Multi-Beam Spaceborne Radiometers
- 2015
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Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856
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Konferensbidrag (refereegranskat)abstract
- Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phasedarray antenna systems designed to operate as focal plane arrays (FPA) in push-broom radiometers. This algorithm is formulated as an optimization procedure that maximizes the beam efficiency, while minimizing the side-lobe and cross- Polarization power inthe area of Earth, subject to a constraint on the beamformer dynamic range. The proposed algorithm is applied to a FPA feeding a torus reflector antenna (designed under the contract with the European Space Agency) and tested for multiple beams. The results demonstrate an improved performance in terms of the optimized beam characteristics, yielding much higher spatial and radiometric resolution as well as much closer distance to coast, as compared to the present-day systems.
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| 4. |
- Iupikov, Oleg, 1983, et al.
(författare)
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Multibeam Focal Plane Arrays with Digital Beamforming for High Precision Space-Borne Ocean Remote Sensing
- 2018
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 66:2, s. 737-748
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Tidskriftsartikel (refereegranskat)abstract
- The present-day ocean remote sensing instruments that operate at low microwave frequencies are limited in spatial resolution and do not allow for monitoring of the coastal waters. This is due to the difficulties of employing a large reflector antenna on a satellite platform, and generating high-quality pencil beams at multiple frequencies. Recent advances in digital beamforming focal-plane arrays (FPAs) have been exploited in this paper to overcome the above problems. A holistic design procedure for such novel multibeam radiometers has been developed, where: 1) the antenna system specifications are derived directly from the requirements to oceanographic surveys for future satellite missions and 2) the numbers of FPA elements/receivers are determined through a dedicated optimum beamforming procedure minimizing the distance to coast. This approach has been applied to synthesize FPAs for two alternative radiometer systems: a conical scanner with an offset parabolic reflector and a stationary wide-scan torus reflector system, each operating at C -, X-, and Ku-bands. Numerical results predict excellent beam performance for both systems with as low as 0.14% total received power over the land.
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| 5. |
- Pontoppidan, Katrine, 1976
(författare)
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Factors Influencing Phytate Degradation in Piglets. Feed phytate behaviour and degradation by microbial phytases
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phytate, the main storage form of phosphorus (P) in plant feedstuffs, is indigestible for monogastric animals, and phytases are therefore used as feed additives to increase the digestibility of phytate-P and limit the inclusion of inorganic P. However, new and improved phytases are needed to obtain better phytate digestibility and allow for lower inclusions of inorganic P.The overall aim was to identify factors influencing phytate degradation in piglets as a means to develop improved phytases. The main part of the work therefore focussed on studying the in vitro and in vivo behaviour of feed phytate (soy/maize) and its degradation by microbial phytases (P. lycii and an experimental bacterial phytase).Pelleting and extrusion cooking only slightly affected the composition of inositol phosphates in feedstuffs. Phytate in soybean and maize meal precipitated with protein at pH below 4.0 and with minerals at pH above 4.5, and calcium critically increased the formation of phytate-mineral complexes. Both phytases demonstrated mainly 6-phytase activity when using Na-phytate as substrate in a simple buffered assay, but they showed different degradation pathways. Interestingly the bacterial phytase degraded InsP6 to InsP4 faster than the P. lycii phytase. During simulated digestion of a soybean-maize meal blend both phytases degraded phytate efficiently. The main difference also in this system was that the bacterial phytase was faster than the P. lycii phytase at degrading InsP6 to InsP4. In piglets, the bacterial phytase demonstrated double phytate degrading activity per unit of enzyme compared to the P. lycii phytase mainly due to superior survival during gastric digestion. Higher solubility of InsP4-InsP3 compared to InsP6-InsP5, together with the fact that InsP3-InsP5 was degraded in the small intestine, indicated that the bacterial phytase may also have an advantage of quickly producing InsP4. A high rate of gastric emptying was found to be limiting for phytate degradation in vivo, but supplying 50,000 FTU kg-1 DM partly overcame this limitation.Phosphorus was absorbed in the small intestine, but potential absorption of inositol phosphates measured as plasma InsP level could not be detected. Overall this work shows that in the search for new phytases, it is important to evaluate phytate degradation at the right conditions. In vitro assays should therefore carefully be adjusted with respect to e.g. substrate, pH, digestive proteases and mineral and protein content. Gastric stability and the speed at which certain inositol phosphates are degraded were found to be important factors for the efficacy of a phytase in vivo. However, a high rate of gastric emptying and the dosage of phytase seem to be the main determining factors for phytate degradation in piglets.
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| 6. |
- Pontoppidan, Katrine, 1976, et al.
(författare)
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Interaction of phytate with protein and minerals in a soybean-maize meal blend depends on pH and calcium addition
- 2007
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 87:10, s. 1886-1892
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate possible interactions of phytate with protein and minerals in simplified animal diets, studies were conducted on the solubility of endogenous phytate, protein and essential minerals in a soybean-maize meal blend within a physiological relevant pH range. The blend was mixed with water for 10 min and then allowed to incubate at 40 degrees C (30 min) after adjustment of the pH. Finally, soluble phytate, protein, zinc, manganese and iron were determined. Phytate and mineral solubility was highly influenced by pH whereas protein solubility was less affected. Addition of 5 g Ca2+ kg(-1) drastically reduced the solubility of phytate, zinc, manganese and iron at pH above 4.4, indicating that the formation of insoluble phytate-mineral complexes is increased in the presence of calcium. The action of pepsin increased the solubility of protein and phytate at pH below 4, indicating that insoluble phytate-protein complexes are present at low pH. Calcium had the same solubilising effect as pepsin at pH 2-4 but to a lesser degree.
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| 7. |
- Pontoppidan, Katrine, 1976, et al.
(författare)
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Peniophora lycii phytase is stabile and degrades phytate and solubilises minerals in vitro during simulation of gastrointestinal digestion in the pig
- 2007
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 1097-0010 .- 0022-5142. ; 87:14, s. 2700-2708
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Microbial phytases (EC 3.1.3) are widely used in diets for monogastric animals to hydrolyse phytate present in the feed and thereby increase phosphorus and mineral availability. Previous work has shown that phytate solubility is strongly affected by calcium in the feed and by pH in the gastrointestinal (GI) tract, which may have an effect on phytase efficacy. An in vitro model simulating the GI tract of pigs was used to study the survival of Peniophora lycii phytase and the effect of the phytase on phytate degradation, inositol phosphate formation and mineral solubilisation during in vitro digestion of a 30:70 soybean meal/maize meal blend with different calcium levels.RESULTS: The phytase retained 76 and 80% of its initial activity throughout the gastric in vitro digestion. Total phytate hydrolysis by P. lycii phytase was in the same range at total calcium levels of 1.2 and 6.2 mg g(-1) dry matter (DM), despite very large differences in phytate solubility at these calcium levels. However, at 11.2 and 21.2 mg Ca g(-1) DM, phytate hydrolysis was significantly lower. The amount of soluble mineral was generally increased by P. lycii phytase.CONCLUSION: Stability of P. lycii phytase during gastric digestion was not found to be critical for phytate hydrolysis. Furthermore, original phytate solubility was not an absolute requirement for phytate degradation; phytate solubility seemed to be in a steady state, allowing insoluble phytate to solubilise as soluble phytate was degraded. This is new and interesting knowledge that adds to the current understanding of phytate-phytase interaction.
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| 8. |
- Pontoppidan, Katrine, 1976, et al.
(författare)
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The type of thermal feed treatment influences the inositol phosphate composition
- 2007
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Ingår i: Animal Feed Science and Technology. - : Elsevier BV. - 0377-8401. ; 132:1-2, s. 137-147
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Tidskriftsartikel (refereegranskat)abstract
- The content and composition of inositol phosphate phosphorus (InsP-P) in maize, wheat, barley and heat treated soybean meal, rapeseed meal and sunflower meal was determined by high-performance ion chromatography (HPIC). Approximately 0.88-0.96 of the InsP-P in the feedstuffs was present in the inositol hexaphosphate (InsP(6)) form, whereas the rest was in the inositol pentaphosphate (InsP(5)) form and for oilseeds a very small amount was present as inositol tetraphosphaie (InSP4). Rapeseed differed from this pattern by having as much as 300 and 609 InsP(4)-P/kg of the total InsP-P pool. The effect of pelleting (90 degrees C) and extrusion cooking (130-140 degrees C, 6.5 MPa) or. the composition of lnsP-P was investigated. Neither treatment had any major effect on the total content of InsP-P in the feedstuffs. However, as indicated by the statistically significant effects on the proportion of the inositol phosphates, extrusion cooking shifted the inositol phosphates from InsP(6)-P towards InSP5-P both in cereals (P=0.002) and in oilseeds (P
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| 9. |
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| 10. |
- Skou, N., et al.
(författare)
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Ultra-High-Performance C-and L-Band Radiometer System for Future Spaceborne Ocean Missions
- 2019
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Ingår i: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. - 2151-1535 .- 1939-1404. ; 12:6, s. 1670-1678
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Tidskriftsartikel (refereegranskat)abstract
- A next-generation real-Aperture spaceborne radiometer system for high-quality ocean measurements is discussed. Instead of illuminating the antenna reflector by a classical feed array of horn antennas in a one-feed-per-beam configuration, a multi-feed-per-beam configuration is chosen. Each antenna beam is thus created by adding the outputs from many small antenna elements in the feed array, thus providing an antenna beam of unsurpassed quality. This solves the classical polarization purity and land/sea contamination issues. The concept requires many microwave receivers and fast analog-To-digital converters as well as fast digital signal processing onboard the satellite. This is discussed, and resource budgets, especially concerning power, are provided.
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