| 1. |
- Belitsky, Victor, 1955, et al.
(författare)
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A new 3 mm band receiver for the Onsala 20 m antenna
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
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Tidskriftsartikel (refereegranskat)abstract
- A new receiver for the Onsala 20 m antenna with the possibility of being equipped with 3 mm and 4 mm bands has been built and the 3 mm channel has been commissioned during the Spring 2014. For single-dish operation, the receiver uses an innovative on-source/off-source optical switch. In combination with additional optical components and within the same optical layout, the switch provides two calibration loads (for the 3 mm and 4 mm channels), sideband rejection measurement, and tuning possibilities. The optical layout of the receiver employs all cold (4 K) offset elliptical mirrors for both channels, whereas the on-off switch employs flat mirrors only. The 3 mm channel employs a sideband separation (2SB) dual polarization receiver with orthomode transducer (OMT), 4-8 GHz intermediate frequency (IF), x? 2pol x? upper and lower sidebands (USB? +? LSB). The cryostat has four optical windows made of high density polyethylene (HDPE) with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat uses a two-stage cryocooler produced by Sumitomo HI? RDK? 408D2 with anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The local oscillator (LO) system is based on a Gunn oscillator with aphase lock loop (PLL) and four mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. This paper provides a technical description of the receiver and its technology and could be useful for instrumentation engineers and observers using the Onsala 20 m telescope.
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| 2. |
- Lapkin, Igor, 1963, et al.
(författare)
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Dual Band MM-Wave Receiver for Onsala 20 m Antenna
- 2014
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Ingår i: Proceedings of the TWENTY-FIFTH INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY, April 27-30, 2014, Moscow, Russia. ; , s. 132-
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Konferensbidrag (refereegranskat)abstract
- We present the design and the first light results for the new dual band receiver (4 mm and 3 mm bands) for Onsala Observatory 20 m antenna. For single dish operation, the receiver uses innovative on-source/off-source optical switch. Within the same optical layout, the switch, in combination with additional optical components, provides 2 calibration loads and sideband measurements possibilities. The optics layout of the receiver uses offset elliptical cold mirrors for both channels whereas the on-off switch employs flat mirrors only. The 3 mm channel employs 2SB dual polarization receiver with OMT, 4-8 GHz IF, x 2pol x (USB+LSB). The cryostat has 4 optical widows made of HDPE with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat employs a two stage cryocooler RDK 408D2 and uses anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The LO system is based on Gunn oscillator with PLL and two mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. At the conference, we will present details on the receiver optics, cryostat design and the result of the first on-sky observations.
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| 3. |
- Aguilera, Guillermo, et al.
(författare)
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Intensive management reduces butterfly diversity over time in urban green spaces
- 2019
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Ingår i: Urban Ecosystems. - : Springer Science and Business Media LLC. - 1083-8155 .- 1573-1642. ; 22:2, s. 335-344
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Tidskriftsartikel (refereegranskat)abstract
- Loss and fragmentation of semi-natural grasslands have had negative consequences for grassland biodiversity, such as butterflies. Urban parks and other urban green spaces have so far largely been overlooked as suitable butterfly habitats, although they could potentially sustain diverse butterfly populations over time. We analysed the temporal change in butterfly species assemblages in urban green spaces in the city of Malmö, Southern Sweden. We studied changes in species richness and abundance of butterflies between 2006 and 2015 in 20 public urban green spaces, characterized by different management regimes. We sampled butterflies in traditional parks with intense grass cutting regimes, in semi-natural grasslands mowed only a few times per year, and in un-managed or irregularly managed ruderal sites. We found a slight increase in the total number of butterfly species in the study area, but a general decline in local species numbers in urban green spaces. Traditional urban parks had the greatest loss of species over time, and altogether the lowest number of species. In contrast, semi-natural parks and ruderal sites had higher numbers of butterfly species and also lost fewer species over time. Our study shows that intensive management strategies in urban green spaces have a negative impact on butterfly assemblages over time. We suggest that less intensive management strategies can be used to create high-quality areas for flower-visiting insects in urban green spaces, possibly in combination with planting larval host plant species, depending on the park type and design.
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| 4. |
- Eilers, Silke, et al.
(författare)
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Micro-climate determines oviposition site selection and abundance in the butterfly Pyrgus armoricanus at its northern range margin
- 2013
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Ingår i: Ecological Entomology. - : Wiley. - 1365-2311 .- 0307-6946. ; 38:2, s. 183-192
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Tidskriftsartikel (refereegranskat)abstract
- 1. Knowledge about species habitat requirements is important when designing conservation strategies as well as for predicting species distributions. For herbivorous insects, insights in oviposition preferences can provide important information on their habitat requirements. 2. The oviposition preferences of Oberthür's Grizzled Skipper butterfly Pyrgus armoricanus Oberthür at its northern range boundary in southern Sweden were studied and it was also tested to what extent oviposition preferences can predict variation in population size among monitored sites. 3. Oviposition behaviour was observed and analysed using a two-step approach. First the characteristics of host plant ramets that female butterflies inspected for oviposition (including both ramets that were rejected and ramets used for oviposition) were compared with with control ramets. Second, ramets on which female butterflies oviposited were compared with ramets that butterflies inspected but rejected. 4. The preferred plant species for oviposition was Filipendula vulgaris Moench. Filipendula vulgaris ramets inspected for oviposition by P. armoricanus females were situated in warm microclimates, primarily on south facing slopes, surrounded by lower vegetation and a higher percentage cover of bare ground compared with random control ramets. 5. Among the inspected ramets, females chose to oviposit those situated in the warmest micro-climates and those surrounded by the largest percentage cover of bare ground. 6. Together with habitat patch area, oviposition preferences explained 65% of the variation in butterfly population size. 7. These results reveal the importance of a microclimate as a component of habitat quality for insect populations at the margins of their geographical range.
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| 5. |
- Gallo, Paola, et al.
(författare)
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Water : A Tale of Two Liquids
- 2016
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Ingår i: Chemical Reviews. - : American Chemical Society (ACS). - 0009-2665 .- 1520-6890. ; 116:13, s. 7463-7500
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Forskningsöversikt (refereegranskat)abstract
- Water is the most abundant liquid on earth and also the substance with the largest number of anomalies in its properties. It is a prerequisite for life and as such a most important subject of current research in chemical physics and physical chemistry. In spite of its simplicity as a liquid, it has an enormously rich phase diagram where different types of ices, amorphous phases, and anomalies disclose a path that points to unique thermodynamics of its supercooled liquid state that still hides many unraveled secrets. In this review we describe the behavior of water in the regime from ambient conditions to the deeply supercooled region. The review describes simulations and experiments on this anomalous liquid. Several scenarios have been proposed to explain the anomalous properties that become strongly enhanced in the supercooled region. Among those, the second critical-point scenario has been investigated extensively, and at present most experimental evidence point to this scenario. Starting from very low temperatures, a coexistence line between a high-density amorphous phase and a low-density amorphous phase would continue in a coexistence line between a high-density and a low-density liquid phase terminating in a liquid liquid critical point, LLCP. On approaching this LLCP from the one-phase region, a crossover in thermodynamics and dynamics can be found. This is discussed based on a picture of a temperature-dependent balance between a high-density liquid and a low-density liquid favored by, respectively, entropy and enthalpy, leading to a consistent picture of the thermodynamics of bulk water. Ice nucleation is also discussed, since this is what severely impedes experimental investigation of the vicinity of the proposed LLCP. Experimental investigation of stretched water, i.e., water at negative pressure, gives access to a different regime of the complex water diagram. Different ways to inhibit crystallization through confinement and aqueous solutions are discussed through results from experiments and simulations using the most sophisticated and advanced techniques. These findings represent tiles of a global picture that still needs to be completed. Some of the possible experimental lines of research that are essential to complete this picture are explored.
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| 6. |
- Harris, Sanna, et al.
(författare)
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Changes in behavioural trait integration following rapid ecotype divergence in an aquatic isopod.
- 2011
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 24, s. 1887-1896
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Tidskriftsartikel (refereegranskat)abstract
- Colonization of new habitats can relax selection pressures, and traits or trait combinations no longer selected for might become reduced or lost. We investigated behavioural differentiation and behavioural trait integration in the freshwater isopod Asellus aquaticus. This isopod has recently colonized a novel habitat and diverged into two ecotypes which encounter different predator faunas. We investigated sex-specific behavioural differences and phenotypic integration in three behavioural assays: (i) time to emerge (TE) from a shelter, (ii) activity and (iii) escape behaviour. General activity and escape behaviour differed between ecotypes. Furthermore, general activity and TE differed between sexes. Behavioural traits were more frequently correlated in the ancestral habitat, and phenotypic integration tended to be higher in this habitat as well. Our study suggests that different predator types, but also other ecological factors such as habitat matrices and population densities, might explain the differences in behavioural integration in these ecotypes.
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| 7. |
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| 8. |
- Karatzas, Xanthias, et al.
(författare)
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Zone-coated Rh-based monolithic catalyst for autothermal reforming of diesel
- 2011
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Ingår i: Applied Catalysis B. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 101:3-4, s. 226-238
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present results of hydrogen generation from diesel via autothermal reforming (AIR) obtained with monolithic catalysts consisting of either one or two layers of monometallic Rh and bimetallic RhPt washcoats. The Rh metal loading of the monometallic washcoats was varied between 0.5, 1.0 and 3.0 wt%, while the weight ratio of Rh:Pt in the bimetallic washcoats was kept constant at 1:1. Furthermore, non-doped and CeLa-doped catalysts were also tested to detect differences in catalyst activity. The catalysts consisting of two layers of washcoats were termed zoned catalysts and each layer was applied to some given length in the axial direction of the monolith. All catalysts were prepared by impregnation using the incipient wetness technique with delta-Al2O3 B as support and deposited onto 400 cpsi cordierite monoliths. A total of eight catalysts, including both single layered and zone-coated, were tested in a bench-scale reactor using low-sulfur diesel as fuel at operating conditions H2O/C=2.5, O-2/C=0.49 (lambda = 0.33), GHSV 17,000 h(-1) and P = 1 atm. The results showed that the zoned catalyst, covered with the two washcoats Rh1.0Pt1.0-Ce10La5.0/delta-Al2O3 and Rh-3.0-Ce10La10/delta-Al2O3, respectively, was most active in terms of fuel conversion and hydrogen production. The zoned catalyst's long-term performance and stability was also evaluated in a full-scale reactor using low-sulfur and Fischer-Tropsch diesels at operating conditions H2O/C = 2.5, O-2/C = 0.49 (lambda =0.33), GHSV= 10,800 h(-1), P = 1 atm, and at H2O/C = 2.4, 02/C = 0.39 (lambda=0.26), GHSV- 10,200 h(-1), P = 1 atm. respectively. The results showed that high fuel conversion and hydrogen production were obtained from both fuels. In addition, partial oxidation and steam reforming reactions were identified by closely studying the distribution of the analyzed product gas composition and the temperature measurements. Fresh and aged samples of the catalysts were characterized by N-2-BET, H-2 chemisorption, XRD, H-2-TPR, O-2-TPO and XPS analyses.
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| 9. |
- Karlsson Green, K, et al.
(författare)
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Rapid changes in genetic architecture of behavioural syndromes following colonization of a novel environment.
- 2016
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Ingår i: Journal of evolutionary biology. - : Wiley. - 1420-9101 .- 1010-061X. ; 29:1, s. 144-152
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Tidskriftsartikel (refereegranskat)abstract
- Behavioural syndromes, that is correlated behaviours, may be a result from adaptive correlational selection, but in a new environmental setting, the trait correlation might act as an evolutionary constraint. However, knowledge about the quantitative genetic basis of behavioural syndromes, and the stability and evolvability of genetic correlations under different ecological conditions, is limited. We investigated the quantitative genetic basis of correlated behaviours in the freshwater isopod Asellus aquaticus. In some Swedish lakes, A. aquaticus has recently colonized a novel habitat and diverged into two ecotypes, presumably due to habitat-specific selection from predation. Using a common garden approach and animal model analyses, we estimated quantitative genetic parameters for behavioural traits and compared the genetic architecture between the ecotypes. We report that the genetic covariance structure of the behavioural traits has been altered in the novel ecotype, demonstrating divergence in behavioural correlations. Thus, our study confirms that genetic correlations behind behaviours can change rapidly in response to novel selective environments.
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| 10. |
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