| 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. |
- Charpentier Ljungqvist, Fredrik, 1982-
(författare)
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Kungamakten och lagen : En jämförelse mellan Danmark, Norge och Sverige under högmedeltiden
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The dissertation is a comparative study of the expansion of law-regulated royal power in Denmark, Norway, and Sweden c. 1150–1350. The aim is to examine how the king’s judicial and military authority and functions, and their effect on the power position of the regional legal assembly and the church, is expressed and how it changed over time in the extant law material. The starting point is the pan-European consolidation of royal power in the High Middle Ages, and the dissertation considers international research on the medieval state formation process and its driving forces. The processual concepts of centralization, institutionalization, hierarchization, and territorialization occupy a central place in the analysis.Danish, Norwegian, and Swedish laws all reflect a significant increase in royal power. A growing number of societal functions were vested in the increasingly institutionalized kingship, and there was a growth in its power resources. At the same time, it is possible to identify crucial inter-Scandinavian differences. A main finding is that the law-regulated royal power, in most respects, was strongest in Norway and weakest in Sweden. Another important conclusion is that executive royal power first emerged after the judicial and also legislative power had already to a large extent come under royal control.It is demonstrated that Scandinavian kingship in the High Middle Ages was characterized by increasingly centralized and institutionalized territorially based power, with a greater monopoly on the use of legitimate force, and thereby strengthened the ongoing state formation process. The expansion of law-regulated royal power primarily concerned the judicial sphere and only secondarily the military and fiscal spheres. That state formation was driven by judicial development rather than militarization is also shown by the fact that Norway, despite having the least professionalized and resource-demanding armed forces, was the Scandinavian country with the most centralized and institutionalized royal power.
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| 3. |
- Elmstedt, Nina, et al.
(författare)
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Fetal cardiac muscle contractility decreases with gestational age : a color-coded tissue velocity imaging study
- 2012
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Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 10, s. 19-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Present data regarding how the fetal heart works and develops throughout gestation is limited. However, the possibility to analyze the myocardial velocity profile provides new possibilities to gain further knowledge in this area. Thus, the objective of this study was to evaluate human fetal myocardial characteristics and deformation properties using color-coded tissue velocity imaging (TVI). Methods: TVI recordings from 55 healthy fetuses, at 18 to 42 weeks of gestation, were acquired at a frame rate of 201-273 frames/s for offline analysis using software enabling retrieval of the myocardial velocity curve and 2D anatomical information. The measurements were taken from an apical four-chamber view, and the acquired data was correlated using regression analysis. Results: Left ventricular length and width increased uniformly with gestational age. Atrioventricular plane displacement and the E'/A' ratio also increased with gestational age, while a longitudinal shortening was demonstrated. Conclusions: Fetal cardiac muscle contractility decreases with gestational age. As numerous fetal-and pregnancy-associated conditions directly influence the pumping function of the fetal heart, we believe that this new insight into the physiology of the human fetal cardiovascular system could contribute to make diagnosis and risk assessment easier and more accurate.
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| 4. |
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| 5. |
- Elmstedt, Nina, et al.
(författare)
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Reference values for fetal tissue velocity imaging and a new approach to evaluate fetal myocardial function
- 2013
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Ingår i: Cardiovascular Ultrasound. - : Springer Science and Business Media LLC. - 1476-7120. ; 11:1, s. 29-
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Myocardial function can be evaluated using color-coded tissue velocity imaging (TVI) to analyze the longitudinal myocardial velocity profile, and by expressing the motion of the atrioventricular plane during a cardiac cycle as coordinated events in the cardiac state diagram (CSD). The objective of this study was to establish gestational age specific reference values for fetal TVI measurements and to introduce the CSD as a potential aid in fetal myocardial evaluation. Methods: TVI recordings from 125 healthy fetuses, at 18 to 42 weeks of gestation, were performed with the transducer perpendicular to the apex to provide a four-chamber view. The myocardial velocity data was extracted from the basal segment of septum as well as the left and right ventricular free wall for subsequent offline analysis. Results: During a cardiac cycle the longitudinal peak velocities of septum increased with gestational age, as did the peak velocities of the left and right ventricular free wall, except for the peak velocity of post ejection. The duration of rapid filling and atrial contraction increased during pregnancy while the duration of post ejection decreased. The duration of pre ejection and ventricular ejection did not change significantly with gestational age. Conclusion: Evaluating fetal systolic and diastolic performance using TVI together with CSD could contribute to increase the knowledge and understanding of fetal myocardial function and dysfunction. The pre and post ejection phases are the variables most likely to indicate fetuses with abnormal myocardial function.
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| 6. |
- Elmstedt, Nina, et al.
(författare)
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Reproducibility and variability in the assessment of color-coded tissue velocity imaging of the fetal myocardium
- 2013
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Ingår i: Journal of biomedical graphics and computing. - : Sciedu Press. - 1925-4008 .- 1925-4016. ; 3:2
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The introduction of color-coded tissue velocity imaging (TVI) in fetal medicine is quite recent, and as this method is presently evaluated and developed in regard to diagnostic precision it is of outmost importance to evaluate the reproducibility for adequate clinical use. In this study, reproducibility and intra- and inter-observer variability was assessed for offline analysis as well as echocardiography investigations. Also, we evaluated the importance of exact placement of the region of interest (ROI).Methods: TVI recordings from 21 fetuses, at a gestational age of 27 to 41 weeks, were acquired at 208-239 frames/s for subsequent offline analysis. All recordings were performed with the transducer positioned to provide an apical four-chamber view and the myocardial velocity data was obtained from basal inferoseptum. The data set was analyzed according to Bland-Altman and reproducibility was expressed as the standard error of a single determination, estimated from duplicate determinations in percentage of the total.Results: The variation of reproducibility for the echocardiography investigation ranged from 2.0% to 9.8%. The duration of left ventricular ejection, and the peak velocities of early diastolic filling and atrial contraction being the most robust events measured. The variation of inter-observer variability for the echocardiography investigation ranged from 1.5% to 8.4%, and the variation of intra- and inter-observer variability for the offline analysis ranged from 1.2% to 10.4%. Least robust were the events of shortest duration, including isovolumetric contraction and relaxation.Conclusion: We believe that TVI measurements of the fetal myocardium could be performed in the clinical routine with acceptable reproducibility.
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| 7. |
- Elmstedt, Nina, et al.
(författare)
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Temporal frequency requirements for tissue velocity imaging of the fetal heart
- 2011
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Ingår i: Ultrasound in Obstetrics and Gynecology. - : Wiley. - 0960-7692 .- 1469-0705. ; 38:4, s. 413-417
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Tidskriftsartikel (refereegranskat)abstract
- Objectives The high velocity and short duration of myocardial motion requires a high sampling rate to obtain adequate temporal resolution; this issue becomes even more important when taking into consideration the high fetal heart rate. In this study we have established optimal sampling requirements for assessing the duration of various cardiac cycle events and myocardial velocities of the fetal heart using color-coded tissue velocity imaging (TVI). Methods Recordings from 30 fetuses were acquired at an initial frame rate of 180-273 frames/s. All TVI recordings were performed from an apical four-chamber view and stored as cineloops of five to 10 consecutive cardiac cycles for subsequent offline analysis using software enabling a reduction in frame rate. Different components of the myocardial velocity curve, obtained from the basal part of the ventricular septum, were measured at the initial frame rate and compared with their equivalents at gradually decreased frame rates. Results As acquisition frame rate was reduced, there was a marked increase in deviation from the initial values, resulting in an underestimation of all systolic and diastolic velocities. For the measured durations, there was a clear tendency to underestimate isovolumetric contraction and relaxation, and a clear tendency to overestimate ventricular ejection and diastolic E-wave and A-wave. An acceptable <= 5% deviation from the value obtained at the highest frame rate corresponded to measurements obtained at above 150-200 frames/s. Conclusions A high sampling rate of at least 200 frames/s is necessary for adequate reconstruction of TVI data for the fetal heart. Frame rates that are too low result in considerable loss of temporal and velocity information.
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| 8. |
- Engblom, Stefan, et al.
(författare)
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Simulation of stochastic reaction-diffusion processes on unstructured meshes
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Stochastic chemical systems with diffusion are modeled with a reaction-diffusion master equation. On a macroscopic level, the governing equation is a reaction-diffusion equation for the averages of the chemical species. On a mesoscopic level, the master equation for a well stirred chemical system is combined with Brownian motion in space to obtain the reaction-diffusion master equation. The space is covered by an unstructured mesh and the diffusion coefficients on the mesoscale are obtained from a finite element discretization of the Laplace operator on the macroscale. The resulting method is a flexible hybrid algorithm in that the diffusion can be handled either on the meso- or on the macroscale level. The accuracy and the efficiency of the method are illustrated in three numerical examples inspired by molecular biology.
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