| 1. |
- Akiyama, Kazunori, et al.
(författare)
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First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multiwavelength Observations, Data Processing, and Calibration
- 2022
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 930:2
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Tidskriftsartikel (refereegranskat)abstract
- We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at the position of the supermassive black hole Sagittarius A* (Sgr A*), collected during the 2017 April 5-11 campaign. The observations were carried out with eight facilities at six locations across the globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. The majority of the 1.3 mm emission arises from horizon scales, where intrinsic structural source variability is detected on timescales of minutes to hours. The effects of interstellar scattering on the image and its variability are found to be subdominant to intrinsic source structure. The calibrated visibility amplitudes, particularly the locations of the visibility minima, are broadly consistent with a blurred ring with a diameter of similar to 50 mu as, as determined in later works in this series. Contemporaneous multiwavelength monitoring of Sgr A* was performed at 22, 43, and 86 GHz and at near-infrared and X-ray wavelengths. Several X-ray flares from Sgr A* are detected by Chandra, one at low significance jointly with Swift on 2017 April 7 and the other at higher significance jointly with NuSTAR on 2017 April 11. The brighter April 11 flare is not observed simultaneously by the EHT but is followed by a significant increase in millimeter flux variability immediately after the X-ray outburst, indicating a likely connection in the emission physics near the event horizon. We compare Sgr A*'s broadband flux during the EHT campaign to its historical spectral energy distribution and find that both the quiescent emission and flare emission are consistent with its long-term behavior.
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| 2. |
- Gavali, Hamid, et al.
(författare)
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Outcome of Radical Surgical Treatment of Abdominal Aortic Graft and Endograft Infections Comparing Extra-anatomic Bypass with In Situ Reconstruction : A Nationwide Multicentre Study
- 2021
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Saunders Elsevier. - 1078-5884 .- 1532-2165. ; 62:6, s. 918-926
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Abdominal aortic graft and endograft infection (AGI) is primarily treated by resection of the infected graft and restoration of distal perfusion through extra-anatomic bypass (EAB) or in situ reconstruction/repair (ISR). The aim of this study was to compare these surgical strategies in a nationwide multicentre retrospective cohort study.Methods: The Swedish Vascular Registry (Swedvasc) was used to identify surgically treated abdominal AGIs in Sweden between January 1995 and May 2017. The primary aim was to compare short and long term survival, as well as complications for EAB and ISR.Results: Some 126 radically surgically treated AGI patients were identified – 102 graft infections and 24 endograft infections – treated by EAB: 71 and ISR: 55 (23 neo-aorto-iliac systems, NAISs). No differences in early 30 day (EAB 81.7% vs. ISR 76.4%, p =.46), or long term five year survival (48.2% vs. 49.9%, p =.87) were identified. There was no survival difference comparing NAIS to other ISR strategies. The frequency of recurrent graft infection during follow up was similar: EAB 20.3% vs. ISR 17.0% (p =.56). Survival and re-infection rates of the new conduit did not differ between NAIS and other ISR strategies. Age ≥ 75 years (odds ratio [OR] 4.0, confidence interval [CI] 1.1 – 14.8), coronary artery disease (OR 4.2, CI 1.2 – 15.1) and post-operative circulatory complications (OR 5.2, CI 1.2 – 22.5) were associated with early death. Prolonged antimicrobial therapy (> 3 months) was associated with reduced long term mortality (HR 0.3, CI 0.1 – 0.9).Conclusion: In this nationwide multicentre study comparing outcomes of radically treated AGI, no differences in survival or re-infection rate could be identified comparing EAB and ISR.
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| 3. |
- Gavali, Hamid, et al.
(författare)
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Semi-Conservative Treatment Versus Radical Surgery in Abdominal Aortic Graft and Endograft Infections
- 2023
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier. - 1078-5884 .- 1532-2165. ; 66:3, s. 397-406
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Abdominal aortic graft and endograft infections (AGIs) are rare complications following aortic surgery. Radical surgery (RS) with resection of the infected graft and reconstruction with extra-anatomical bypass or in situ reconstruction is the preferred therapy. For patients unfit for RS, a semi-conservative (SC), graft preserving strategy is possible. This paper aimed to compare survival and infection outcomes between RS and SC treatment for AGI in a nationwide cohort.Methods: Patients with abdominal AGI related surgery in Sweden between January 1995 and May 2017 were identified. The Management of Aortic Graft Infection Collaboration (MAGIC) criteria were used for the definition of AGI. Multivariable regression was performed to identify factors associated with mortality.Results: One hundred and sixty-nine patients with surgically treated abdominal AGI were identified, comprising 43 SC (14 endografts; 53% with a graft enteric fistula [GEF] in total) and 126 RS (26 endografts; 50% with a GEF in total). The SC cohort was older and had a higher frequency of cardiac comorbidities. There was a non-significant trend towards lower Kaplan -Meier estimated five year survival for SC vs. RS (30.2% vs. 48.4%; p = .066). A non-significant trend was identified towards worse Kaplan -Meier estimated five year survival for SC patients with a GEF vs. without a GEF (21.7% vs. 40.1%; p = .097). There were significantly more recurrent graft infections comparing SC with RS (45.4% vs. 19.3%; p < .001). In a Cox regression model adjusting for confounders, there was no difference in five year survival comparing SC vs. RS (HR 1.0, 95% CI 0.6 -1.5).Conclusion: In this national AGI cohort, there was no mortality difference comparing SC and RS for AGI when adjusting for comorbidities. Presence of GEF probably negatively impacts survival outcomes of SC patients. Rates of recurrent infection remain high for SC treated patients.
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| 4. |
- Gavali, Hamid, et al.
(författare)
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Semi-Conservative Treatment Versus Surgery in Abdominal Aortic Graft and Endograft Infections
- 2023
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Ingår i: European Journal of Vascular and Endovascular Surgery. - : Elsevier. - 1078-5884 .- 1532-2165. ; 66:3, s. 397-406
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Abdominal aortic graft and endograft infections (AGIs) are rare complications following aortic surgery. Radical surgery (RS) with resection of the infected graft and reconstruction with extra-anatomical bypass or in situ reconstruction is the preferred therapy. For patients unfit for RS, a semi-conservative (SC), graft-preserving strategy is possible. This paper aimed to compare survival and infection outcomes between RS and SC treatment for AGI in a nationwide cohort.METHODS: Patients with abdominal AGI-related surgery in Sweden between January 1995 and May 2017 were identified. The Management of Aortic Graft Infection Collaboration (MAGIC) criteria were used for definition of AGI. Multivariable regression was performed to identify factors associated with mortality.RESULTS: A total of 169 patients with surgically treated abdominal AGI were identified, comprising 43 SC [14 endografts; 53% with a graft-enteric fistula (GEF) in total] and 126 RS [26 endografts; 50% with a GEF in total]. The SC cohort was older and had a higher frequency of cardiac comorbidities. There was a non-significant trend towards lower Kaplan-Meier estimated 5-year survival for SC versus RS (30.2% vs. 48.4%; p = .066). A non-significant trend was identified towards worse Kaplan-Meier estimated 5-year survival for SC patients with a GEF versus without a GEF (21.7% vs. 40.1%; p = .097). There were significantly more recurrent graft infections comparing SC versus RS (45.4% vs. 19.3%; p < .001). In a Cox regression model adjusting for confounders, there was no difference in 5-year survival comparing SC versus RS (HR 1.0, 95% CI 0.6 - 1.5).CONCLUSION: In this national AGI cohort, we could not identify any mortality difference comparing SC versus RS for AGI when adjusting for comorbidities. Presence of GEF likely negatively impacts survival outcomes of SC patients. Rates of recurrent infection remain high for SC-treated patients.
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| 5. |
- Amani, Payam, et al.
(författare)
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Application of Control Theory to a Commercial Mobile Service Support System
- 2012
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Ingår i: International Journal on Advances in Telecommunications. - 1942-2601. ; 5:3&4
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Tidskriftsartikel (refereegranskat)abstract
- The Mobile Service Support system (MSS), which Ericsson AB develops, handles the setup of new subscribers and services into a mobile network. Experience from deployed systems show that traffic monitoring and control of the system will be crucial for handling overload situations that may occur at sudden traffic surges. In this paper we identify and explore some important control challenges for this type of systems. Further, we present analysis and experiments showing some advantages of proposed solutions. First, we develop a load-dependent server model for the system, which is validated in testbed experiments. Further, we propose a control design based on the model, and a method for estimation of response times and arrival rates. The main contribution of this paper is that we show how control theory methods and analysis can be used for commercial telecom systems. Parts of our results have been implemented in commercial products, validating the strength of our work.
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| 6. |
- Baudry, A., et al.
(författare)
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Vibrationally excited water emission at 658 GHz from evolved stars
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 609
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Tidskriftsartikel (refereegranskat)abstract
- Context. Several rotational transitions of ortho- and para-water have been identified toward evolved stars in the ground vibrational state as well as in the first excited state of the bending mode (v2 = 1 in (0, 1, 0) state). In the latter vibrational state of water, the 658 GHz J = 1 1,0 -1 0,1 rotational transition is often strong and seems to be widespread in late-type stars. Aims. Our main goals are to better characterize the nature of the 658 GHz emission, compare the velocity extent of the 658 GHz emission with SiO maser emission to help locate the water layers and, more generally, investigate the physical conditions prevailing in the excited water layers of evolved stars. Another goal is to identify new 658 GHz emission sources and contribute in showing that this emission is widespread in evolved stars. Methods. We have used the J = 1 1,0 -1 0,1 rotational transition of water in the (0, 1, 0) vibrational state nearly 2400 K above the ground-state to trace some of the physical conditions of evolved stars. Eleven evolved stars were extracted from our mini-catalog of existing and potential 658 GHz sources for observations with the Atacama Pathfinder EXperiment (APEX) telescope equipped with the SEPIA Band 9 receiver. The 13 CO J = 6-5 line at 661 GHz was placed in the same receiver sideband for simultaneous observation with the 658 GHz line of water. We have compared the ratio of these two lines to the same ratio derived from HIFI earlier observations to check for potential time variability in the 658 GHz line. We have compared the 658 GHz line properties with our H 2 O radiative transfer models in stars and we have compared the velocity ranges of the 658 GHz and SiO J = 2-1, v = 1 maser lines. Results. Eleven stars have been extracted from our catalog of known or potential 658 GHz evolved stars. All of them show 658 GHz emission with a peak flux density in the range ≈ 50-70 Jy (RU Hya and RT Eri) to ≈ 2000-3000 Jy (VY CMa and W Hya). Five Asymptotic Giant Branch (AGB) stars and one supergiant (AH Sco) are new detections. Three AGBs and one supergiant (VY CMa) exhibit relatively weak 13 CO J = 6-5 line emission while o Ceti shows stronger 13 CO emission. We have shown that the 658 GHz line is masing and we found that the 658 GHz velocity extent tends to be correlated with that of the SiO maser suggesting that both emission lines are excited in circumstellar layers close to the central star. Broad and stable line profiles are observed at 658 GHz. This could indicate maser saturation although we have tentatively provided first information on time variability at 658 GHz.
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| 7. |
- Belitsky, Victor, 1955, et al.
(författare)
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SEPIA - A new single pixel receiver at the APEX telescope
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 612
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Tidskriftsartikel (refereegranskat)abstract
- Context. We describe the new Swedish-ESO PI Instrument for APEX (SEPIA) receiver, which was designed and built by the Group for Advanced Receiver Development (GARD), at Onsala Space Observatory (OSO) in collaboration with ESO. It was installed and commissioned at the APEX telescope during 2015 with an ALMA Band 5 receiver channel and updated with a new frequency channel (ALMA Band 9) in February 2016. Aim. This manuscript aims to provide, for observers who use the SEPIA receiver, a reference in terms of the hardware description, optics and performance as well as the commissioning results. Methods. Out of three available receiver cartridge positions in SEPIA, the two current frequency channels, corresponding to ALMA Band 5, the RF band 158-211 GHz, and Band 9, the RF band 600-722 GHz, provide state-of-the-art dual polarization receivers. The Band 5 frequency channel uses 2SB SIS mixers with an average SSB noise temperature around 45 K with IF (intermediate frequency) band 4-8 GHz for each sideband providing total 4 × 4 GHz IF band. The Band 9 frequency channel uses DSB SIS mixers with a noise temperature of 75-125 K with IF band 4-12 GHz for each polarization. Results. Both current SEPIA receiver channels are available to all APEX observers.
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| 8. |
- Benesch, Henric, 1972, et al.
(författare)
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Ingreppsfestival
- 2010
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Ingår i: Kanaltorgsgatan, Heurlins plats, Stenpiren, Verkstadsgatan (Göteborg).
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- I samband med det forskningsprojektet Ingrepp genomfördes en Ingreppfestival med avseende på att i ett öppet publikt sammanhang diskutera utgångspunkterna forskningsgruppen formulerat i tabloiden Ingrepp – en tidning om städer, planering och konst, vilket delades ut gratis en vecka innan festivalen. I tidningen hittade man läsning kring städer, stadsutveckling, konst och konstnärlig forskning vilken hade bäring på den utvecklingsprocess som pågick och pågår på Södra Älvstranden i Göteborg. Både tabloiden och festivalen var ett direkt uttryck för gruppen vilja att ta ut diskussionen på gatan och i sitt sammanhang, men också ett sätt att pröva konstens och akademins möjligheter att gripa in och delta i samhälleliga skeenden. Festivalen vilken turnerade runt på fyra platser under fyra dagar längs Södra Älvstranden innefattade allt ifrån inbjudna samtal/debatter/seminarier till workshops kring Södra Älvstrandens framtid till tipspromenader, picnics och olika former av performativa iscensättningar under bar himmel.
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| 9. |
- Bommarco, Riccardo, et al.
(författare)
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Genetic and phenotypic differences between thistle populations in response to habitat and weed management practices
- 2010
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Ingår i: Biological Journal of the Linnean Society. - : Oxford University Press (OUP). - 0024-4066 .- 1095-8312. ; 99:4, s. 797-807
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Tidskriftsartikel (refereegranskat)abstract
- Rapid evolutionary change is increasingly being recognized as commonplace, but the evolutionary consequences for species and ecosystems under human-induced selection regimes have not been explored in detail, although many species occur in such environments. In a common garden experiment and with amplified fragment length polymorphism markers, we examined whether genetic differentiation has taken place between spatially intermixed populations of creeping thistles Cirsium arvense (Asteraceae) collected from a natural habitat (maritime shores), a semi-natural habitat (road verges) and arable fields under two management regimes: conventional and organic farming. Populations of C. arvense have altered genetically and locally adapted their growth patterns with changed land use. Although plants from different habitats showed similar total biomass production, shoot and root production was higher for maritime populations, suggesting selection for increased competitive ability. Competitive ability then declined in the order semi-natural, conventional farms and organic farms. Thistles in arable fields may be more selected for tolerance against disturbances from herbicides and mechanical weed control. In addition, early shoot sprouting and genetic analysis showed differentiation between plants originating from conventional farms and farms that were converted to organic 9–30 years ago, suggesting some adaptation to altered crop cultivation practices
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| 10. |
- Duarte-Cabral, A., et al.
(författare)
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The SEDIGISM survey: Molecular clouds in the inner Galaxy
- 2021
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 500:3, s. 3027-3049
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Forskningsöversikt (refereegranskat)abstract
- We use the 13CO(2-1) emission from the SEDIGISM (Structure, Excitation, and Dynamics of the Inner Galactic InterStellar Medium) high-resolution spectral-line survey of the inner Galaxy, to extract the molecular cloud population with a large dynamic range in spatial scales, using the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm. This work compiles a cloud catalogue with a total of 10 663 molecular clouds, 10 300 of which we were able to assign distances and compute physical properties. We study some of the global properties of clouds using a science sample, consisting of 6664 well-resolved sources and for which the distance estimates are reliable. In particular, we compare the scaling relations retrieved from SEDIGISM to those of other surveys, and we explore the properties of clouds with and without high-mass star formation. Our results suggest that there is no single global property of a cloud that determines its ability to form massive stars, although we find combined trends of increasing mass, size, surface density, and velocity dispersion for the sub-sample of clouds with ongoing high-mass star formation. We then isolate the most extreme clouds in the SEDIGISM sample (i.e. clouds in the tails of the distributions) to look at their overall Galactic distribution, in search for hints of environmental effects. We find that, for most properties, the Galactic distribution of the most extreme clouds is only marginally different to that of the global cloud population. The Galactic distribution of the largest clouds, the turbulent clouds and the high-mass star-forming clouds are those that deviate most significantly from the global cloud population. We also find that the least dynamically active clouds (with low velocity dispersion or low virial parameter) are situated further afield, mostly in the least populated areas. However, we suspect that part of these trends may be affected by some observational biases (such as completeness and survey limitations), and thus require further follow up work in order to be confirmed.
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| 11. |
- Humphreys, E. M., et al.
(författare)
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Simultaneous 183 GHz H2O maser and SiO observations towards evolved stars using APEX SEPIA Band 5
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 603, s. A77-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. The aim is to investigate the use of 183 GHz H2O masers for characterization of the physical conditions and mass loss process in the circumstellar envelopes of evolved stars. Methods. We used APEX SEPIA Band 5 (an ALMA Band 5 receiver on the APEX telescope) to observe the 183 GHz H2O line towards two red supergiant (RSG) and three asymptotic giant branch (AGB) stars. Simultaneously, we observed the J = 4-3 line for (SiO)-Si-28 nu = 0, 1, 2 and 3, and for (SiO)-Si-29 nu = 0 and 1. We compared the results with simulations and radiative transfer models for H2O and SiO, and examined data for the individual linear orthogonal polarizations. Results. We detected the 183 GHz H2O line towards all the stars with peak flux densities >100 Jy, including a new detection from VYCMa. Towards all five targets, the water line had indications of being caused by maser emission and had higher peak flux densities than for the SiO lines. The SiO lines appear to originate from both thermal and maser processes. Comparison with simulations and models indicate that 183 GHz maser emission is likely to extend to greater radii in the circumstellar envelopes than SiO maser emission and to similar or greater radii than water masers at 22, 321 and 325 GHz. We speculate that a prominent blue-shifted feature in the WHya 183 GHz spectrum is amplifying the stellar continuum, and is located at a similar distance from the star as mainline OH maser emission. We note that the coupling of an SiO maser model to a hydrodynamical pulsating model of an AGB star yields qualitatively similar simulated results to the observations. From a comparison of the individual polarizations, we find that the SiO maser linear polarization fraction of several features exceeds the maximum fraction allowed under standard maser assumptions and requires strong anisotropic pumping of the maser transition and strongly saturated maser emission. The low polarization fraction of the H2O maser however, fits with the expectation for a non-saturated maser. Conclusions. 183 GHz H2O masers can provide strong probes of the mass loss process of evolved stars. Higher angular resolution observations of this line using ALMA Band 5 will enable detailed investigation of the emission location in circumstellar envelopes and can also provide information on magnetic field strength and structure.
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| 12. |
- Kronkvist, Karl, 1987-
(författare)
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Locating place, crime and the fear of crime : methodological and theoretical considerations
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Much previous research on the fear of crime has focused on why some individuals, with certain characteristics, experience more or less fear of crime than others. However, there is also a growing body of research examining the role that the neighbourhood context in which individuals reside plays in shaping such feelings and perceptions. At the same time, less research has been directed at understanding why certain small-scale micro-places evoke feelings of unsafety and fear of crime.The aim of this dissertation is to contribute to improving the current state ofthe research focused on place, the fear of crime, and related methodological issues. The dissertation includes four original empirical research papers. Study I is based on a case study evaluating the impact of camera surveillance and examines what role the operationalization of place may play for the results and interpretation of a given study.The findings show that different operationalizations may indeed produce different results, and that the choice of operationalization must be carefully considered in the context of study design. Study II uses responses to an open-ended survey question from three waves of the Malmö Community Survey (2012, 2015, 2018) to chart the spatial concentration and temporal stability of unsafe locations.The findings show that locations perceived as unsafe by city inhabitants are concentrated to a very small proportion of the urban space, and that there is a temporal stability in unsafe locations over time. Study III further explores unsafe locations by examining the spatial risk factors associated with these unsafe locations and the role played by neighbourhood collective efficacy and disorder. The results show that a number of spatial risk factors are correlated with the outcome, suggesting that the physical environment has a role to play in shaping people’s perceptions of unsafety at a given location. The findings also show that there are major between neighbourhood variations in unsafe locations, but that neighbourhood collective efficacy and disorder play only a limited role in the explanation of this variance. The final paper, Study IV, is a methodological study focused on the feasibility of using an alternative approach to studying fear of crime, as a momentary event, and uses an experience research framework implemented using a smart phone application (STUNDA). The general conclusion is that it is feasible to conduct research on the fear of crime using a smartphone application, but that emerging methods may also involve new methodological issues and challenges.The four studies have both methodological and theoretical implications, suggesting that the way place is defined and operationalized may have important impacts on the results and interpretations of research studies. In addition, the findings suggest that there is more to be learned about the fear of crime as a context-specific experience that is dependent on the immediate environment, and that alternative methodological approaches focused on surveying momentary experiences of fear of crime using smartphone applications seem to be feasible. A place-based approach to the fear of crime, supported by alternative measures and methods, may also be important in developing a broader understanding of how perceptions of fear of crime and unsafety are shaped. Such an understanding may in turn assist policymakers and practitioners to design knowledge-based interventions to reduce fear of crime and feelings of unsafety.
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| 13. |
- Kuang, Yubin, et al.
(författare)
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A Complete Characterization and Solution to the Microphone Position Self-Calibration Problem
- 2013
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Ingår i: A. - 1520-6149. ; , s. 3875-3879
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Konferensbidrag (refereegranskat)abstract
- This paper presents a complete characterization and solution to microphone position self-calibration problem for time-of-arrival (TOA) measurements. This is the problem of determining the positions of receivers and transmitters given all receiver-transmitter distances. Such calibration problems arise in application such as calibration of radio antenna networks, audio or ultra-sound arrays and WiFi transmitter arrays. We show for what cases such calibration problems are well-defined and derive efficient and numerically stable algorithms for the minimal TOA calibration problems. The proposed algorithms are non-iterative and require no assumptions on the sensor positions. Experiments on synthetic data show that the proposed minimal solvers are numerically stable and perform well on noisy data. The solvers are also tested on two real datasets with good results.
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| 14. |
- Meledin, Denis, 1974, et al.
(författare)
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SEPIA345: A 345 GHz dual polarization heterodyne receiver channel for SEPIA at the APEX telescope
- 2022
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 668
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Tidskriftsartikel (refereegranskat)abstract
- Context. We describe the new SEPIA345 heterodyne receiver channel installed at the Atacama Pathfinder EXperiment (APEX) telescope, including details of its configuration, characteristics, and test results on sky. SEPIA345 is designed and built to be a part of the Swedish ESO PI Instrument for the APEX telescope (SEPIA). This new receiver channel is suitable for very high-resolution spectroscopy and covers the frequency range 272- 376 GHz. It utilizes a dual polarization sideband separating (2SB) receiver architecture, employing superconductor-isolator-superconductor mixers (SIS), and provides an intermediate frequency (IF) band of 4- 12 GHz for each sideband and polarization, thus covering a total instantaneous IF bandwidth of 4 ÃÂ - 8 = 32 GHz. Aims. This paper provides a description of the new receiver in terms of its hardware design, performance, and commissioning results. Methods. The methods of design, construction, and testing of the new receiver are presented. Results. The achieved receiver performance in terms of noise temperature, sideband rejection, stability, and other parameters are described. Conclusions. SEPIA345 is a commissioned APEX facility instrument with state-of-the-art wideband IF performance. It has been available on the APEX telescope for science observations since July 2021.
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| 15. |
- Meledin, Denis, 1974, et al.
(författare)
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SEPIA345: a dual polarization 2SB cartridge receiver for APEX telescope: Design and Performance
- 2023
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Ingår i: Proceedings of the 32nd IEEE International Symposium on Space THz Technology.
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Konferensbidrag (refereegranskat)abstract
- A new receiver channel covering the 271-377 GHz frequency band has been installed into the SEPIA receiver at the APEX telescope. The receiver channel was designed and built in an ALMA-compatible cartridge layout. The receiver has a dual polarization layout with OMT and employs 2SB SIS mixers featuring an extended 4-12 GHz IF band, providing 32 GHz instantaneous IF bandwidth for two polarizations and two sidebands.
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| 16. |
- Meledin, Denis, 1974, et al.
(författare)
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SEPIA345: a dual polarization 2SB cartridge receiver for APEX telescope: Design and Performance
- 2022
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Ingår i: 32nd International Symposium of Space Terahertz Technology, ISSTT 2022.
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Konferensbidrag (refereegranskat)abstract
- A new receiver channel covering the 271-377 GHz frequency band has been installed into the SEPIA receiver at the APEX telescope. The receiver channel was designed and built in an ALMA-compatible cartridge layout. The receiver has a dual polarization layout with OMT and employs 2SB SIS mixers featuring an extended 4-12 GHz IF band, providing 32 GHz instantaneous IF bandwidth for two polarizations and two sidebands.
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| 17. |
- Oskarsson, Magnus, et al.
(författare)
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Prime Rigid Graphs and Multidimensional Scaling with Missing Data
- 2014
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Ingår i: Pattern Recognition (ICPR), 2014 22nd International Conference on. - 1051-4651. ; , s. 750-755
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate the problem of embedding a number of points given certain (but typically not all) inter-pair distance measurements. This problem is relevant for multi-dimensional scaling problems with missing data, and is applicable within anchor-free sensor network node calibration and anchor-free node localization using radio or sound TOA measurements. There are also applications within chemistry for deducing molecular 3D structure given inter-atom distance measurements and within machine learning and visualization of data, where only similarity measures between sample points are provided. The problem has been studied previously within the field of rigid graph theory. Our aim is here to construct numerically stable and efficient solvers for finding all embeddings of such minimal rigid graphs. The method is based on the observation that all graphs are either irreducibly rigid, here called prime rigid graphs, or contain smaller rigid graphs. By solving the embedding problem for the prime rigid graphs and for ways of assembling such graphs to other minimal rigid graphs, we show how to (i) calculate the number of embeddings and (ii) construct numerically stable and efficient algorithms for obtaining all embeddings given inter-node measurements. The solvers are verified with experiments on simulated data.
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| 18. |
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| 19. |
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| 20. |
- Torstensson, Karl, 1977, et al.
(författare)
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Methanol masers and millimetre lines: a common origin in protostellar envelopes
- 2012
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Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 8:5287, s. 146-150
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Konferensbidrag (refereegranskat)abstract
- To understand the origin of the CH3OH maser emission, we map the distribution and excitation of the thermal CH3OH emission in a sample of 14 relatively nearby (
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| 21. |
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