| 1. |
- Andersson, Erik, 1962-
(författare)
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A Variational data assimilation scheme and its use of meteorological observations
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Meteorological data assimilation is the process by which a model simulation of the atmosphere is corrected by observations. In operational weather forecasting, this is done in near real-time, to provide accurate initial conditions for numerical forecasts. The accuracy of the forecasts depends crucially on the accuracy of the data assimilation.The increase in available computing power and the theoretical advances in data assimilation methods have recently enabled the European Centre for Medium-Range Weather Forecasts (ECMWF) to develop and introduce operationally a new data assimilation scheme (4D-Var), based on variational methods. The four papers of this thesis present recent developments that have exploited some of the most promising possibilities of 4D-Var with respect to observation usage. They have all been incorporated in operational practice at ECMWF.Variational data assimilation schemes have several advantages that make the new scheme more flexible than earlier schemes with respect to the use of observations. The introduction of 4D-Var has enabled the effective use of a wider range of meteorological observations than previously possible. This includes, as will be demonstrated in this thesis, both conventional observations and satellite measurements.In the first paper we develop a method for the use of satellite radiance observations, and investigate the aspects of 4D-Var that make the scheme particularly well suited for the assimilation of data from a growing variety of space based observing systems. In the second paper we develop a variational quality control method. The third paper investigates the flow-dependence of the 4D-Var response to time series of surface pressure observations in the vicinity of a rapidly developing storm. The final paper presents a diagnostic method for tuning of the 4D-Var system.
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| 2. |
- Bengtsson Boström, Kristina, et al.
(författare)
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Polymorphism in the angiotensin converting enzyme but not in the angiotensinogen gene is associated with hypertension and type 2 diabetes: the Skaraborg Hypertension and diabetes project
- 1999
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Ingår i: Journal of Hypertension. - 1473-5598. ; 17:11, s. 1569-1575
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To study the association between polymorphisms in the angiotensin converting enzyme (ACE) gene and angiotensinogen (AGT) gene and hypertension and/or type 2 diabetes in a community population. PATIENTS AND METHODS: The insertion (I)/deletion (D) polymorphism of the ACE gene and the M235T polymorphism of the AGT gene were genotyped in 773 nondiabetic individuals with hypertension, 193 normotensive patients with type 2 diabetes, 243 patients with type 2 diabetes and hypertension, and in 820 normotensive control individuals identified in a community-based study. RESULTS: The DD genotype was associated with hypertension in individuals less than 70 years [odds ratio (OR) = 1.54, confidence interval (CI) = 1.09-2.18] and remained so when patients with type 2 diabetes were excluded from the analysis (OR = 1.45, CI = 1.01-2.09). The strongest association was with the combination of type 2 diabetes and hypertension (OR = 2.19, CI = 1.09-4.38). There was no association with type 2 diabetes without hypertension. No association was observed between the M235T variant or the 3'-microsatellite polymorphism of the AGT gene and hypertension. CONCLUSION: The D-allele of the ACE gene ID polymorphism increases susceptibility to hypertension, particularly when associated with type 2 diabetes. No association was observed between the M235T variant or 3'-microsatellite polymorphism of the AGT gene and hypertension.
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| 3. |
- Bengtsson, Per Erik
(författare)
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Simultaneous two-dimensional visualization of soot and OH in flames using laser-induced fluorescence
- 1996
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Ingår i: Applied Spectroscopy. - 0003-7028. ; 50:9, s. 1182-1186
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional visualization of soot has been realized in flames with the use of laser-induced fluorescence in C2 from laser-vaporized soot [LIF(C2)LVS]. Soot particles are heated to vaporization temperatures by the absorption of laser radiation. C2 radicals produced by this process are excited at wavelengths around 563 nm through the transition ν′ = 0 d3∏g←ν″ = 1 a3∏u, and the subsequent fluorescence at approximately 516 nm is detected. By frequency-doubling of the laser radiation, wavelengths around 281.5 nm are achieved, which can excite OH radicals to the ν′ = 1 A2Σ+ state from ν″ = 0 X2∏, with subsequent fluorescence at approximately 310 nm. With the use of both these excitation wavelengths, and a Cassegrainian split-mirror telescope as the imaging detection system in front of the charge-coupled device (CCD) camera, simultaneous two-dimensional single-shot images of soot and OH were obtained on a single CCD chip, thus enabling both sooting regions and reaction zones in flames to be monitored.
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| 4. |
- Bood, Joakim, et al.
(författare)
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Knock in spark-ignition engines : End-gas temperature measurements using rotational CARS and detailed kinetic calculations of the autoignition process
- 1997
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- Cycle-resolved end-gas temperatures were measured using dual-broadband rotational CARS in a single-cylinder spark-ignition engine. Simultaneous cylinder pressure measurements were used as an indicator for knock and as input data to numerical calculations. The chemical processes in the end-gas have been analysed with a detailed kinetic mechanism for mixtures of iso-octane and n-heptane at different Research Octane Numbers (RON'S). The end-gas is modelled as a homogeneous reactor that is compressed or expanded by the piston movement and the flame propagation in the cylinder. The calculated temperatures are in agreement with the temperatures evaluated from CARS measurements. It is found that calculations with different RON'S of the fuel lead to different levels of radical concentrations in the end-gas. The apperance of the first stage of the autoignition process is marginally influenced by the RON, while the ignition delay of the second stage is increased with increasing RON.
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| 5. |
- Bood, Joakim, et al.
(författare)
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Non-intrusive temperature and oxygen concentration measurements in a catalytic combustor using : Rotational coherent anti-stokes raman spectroscopy
- 1999
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Ingår i: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations. - 9780791878590 ; 2
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Konferensbidrag (refereegranskat)abstract
- Rotational CARS (Coherent anti-Stokes Raman Spectroscopy) was used to measure temperature and relative oxygen concentrations in the exhaust gas of a catalytic combustor. This laser technique has the general advantages of such techniques, i.e. possibility of performing in-situ measurements with high spatial and temporal resolution, and non-intrusiveness. Profiles of temperature and oxygen concentrations are presented for a full-load condition, and the measured temperatures are compared with calculated values. Of great importance for the results is the accuracy of the technique, and a sensitivity analysis is performed to test the temperature and oxygen concentration dependence on uncertainties in experimental parameters. It was shown that the accuracy of temperature and oxygen concentration could be improved by fitting the nonresonant susceptibility in the evaluation procedure. The measurements were performed as a project in the European gas turbine program AGATA with the aim to develop a catalytic combustor with ceramic structural components and producing low emissions of pollutants.
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| 6. |
- Bood, Joakim, et al.
(författare)
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Stray light rejection in rotational coherent anti-Stokes Raman spectroscopy by use of a sodium-seeded flame
- 1998
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Ingår i: Applied Optics. - 1559-128X. ; 37:36, s. 8392-8396
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Tidskriftsartikel (refereegranskat)abstract
- A common experimental problem with rotational coherent anti-Stokes Raman spectroscopy (CARS) is undesired spectral interference that is due to stray light from the primary laser beams. Also, for the most developed approach, dual-broadband rotational CARS, practical measurements often suffer from stray light interference from the narrow-band laser, inasmuch as the CARS signal is produced inherently in the spectral vicinity of the narrow-band laser beam. An optical filter does not provide a sufficiently sharp transmission profile, thus leading to signal loss and spectral distortion of the rotational CARS signal. An atomic filter consisting of a sodium-seeded flame is presented here as a solution to the problem, and its usefulness was demonstrated in dual-broadband rotational CARS experiments.
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| 7. |
- Bøg-Hansen, Erik, et al.
(författare)
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Risk factor clustering in patients with hypertension and non-insulin-dependent diabetes mellitus. The Skaraborg Hypertension Project
- 1998
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Ingår i: Journal of Internal Medicine. - 1365-2796. ; 243:3, s. 223-232
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To assess the coexistence of hypertension and diabetes, associations with cardiovascular risk factors and the achievement of current treatment goals. DESIGN: A community-based, cross-sectional, observational study. SETTING: Hypertension and diabetes outpatient clinics in primary health care, Skara, Sweden. SUBJECTS: All patients (n = 1116; 488 men, 628 women) who performed an annual follow-up from May 1992 to September 1993. MAIN OUTCOME MEASURES: Hypertension, non-insulin-dependent diabetes mellitus (NIDDM), blood pressure, fasting B-glucose, lipids, HbAlc, body mass index (BMI), waist hip ratio (WHR). RESULTS: Hypertension alone was found in 286 men and 430 women, hypertension and NIDDM combined in 102 men and 102 women, and NIDDM alone in 100 men and 96 women. Taking new cases into account, the proportion of hypertension among NIDDM patients was 57%, and the proportion of NIDDM among hypertensives was 26%. Men and women with both hypertension and NIDDM had a higher systolic blood pressure and women also had a higher diastolic blood pressure (men 168/88 mmHg, women 165/86 mmHg) than those with hypertension alone (men 152/87 mmHg, women 156/82 mmHg) (P < or = 0.001). Cardiovascular risk factors accumulated in patients with both hypertension and NIDDM (triglycerides, BMI and WHR). A diastolic blood pressure < or = 90 mmHg was achieved by 71% men and 84% women with hypertension. HbAlc < 7.5% was attained by 71% men and 70% women with NIDDM. CONCLUSIONS: A considerable coexistence of hypertension and NIDDM was demonstrated. Cardiovascular risk factors clustered in patients with both diseases and their blood pressure was less controlled. These patients thus comprised a clinically defined group at high risk. By current guidelines, control of hypertension and NIDDM seemed appropriate.
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| 8. |
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| 9. |
- Larsson, Per-Erik, et al.
(författare)
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Biologiska effekter i kalkad skog. Årsrapport 1998. Effektuppföljning av Skogsstyrelsens program för kalkning och vitaliseringsgödsling av skogsmark.
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Skogsstyrelsens försöksverksamhet med kalkning och vitalisering av skogsmark innehåller ett omfattande program för effektuppföljning. IVL (IVL Svenska Miljöinstitutet AB) i Aneboda har tillsammans med Skogsvårdsstyrelserna huvudansvaret för uppföljningen. Huvuddelen av programmet är inriktat mot effekter på träd, mark och vatten, då kalkning utförts enligt Skogsstyrelsens koncept. Utöver detta basprogram finns även särskilda försök där olika typer av kalk och aska prövas. Resultaten presenteras i årliga rapporter. Tidigare rapporter har behandlat kalkningseffekter på ytvatten och effekter i marken, baserad på markkemiska och markvattenkemiska mätningar. Denna rapport redovisar resultaten från uppföljningsprogrammet för biologiska effekter. Den baseras på undersökningar av bottenfauna, påväxtalger, barrkemi och trädens vitalitet. Studierna är utförda inom Skogsstyrelsens storskaliga försök med skogsmarkskalkning och vitaliseringsgödsling. Rapporten omfattar tidsperioden, eller delar av perioden, 1991 till 1998. Resultaten i sammanfattning är: Bottenfauna. Undersökningen visar att den kalkdos på 3 ton per hektar som använts i försöken inte är tillräcklig för att påverka faunan i kraftigt försurade bäckar under de första sju till åtta åren efter behandling.Någon ökning av antalet individer och taxa eller större biodiversitet har inte kunnat påvisas. Det har heller inte framkommit något som tyder på att faunan har skadats av någon 'kalkchock' eller liknande efter behandlingen
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| 10. |
- Olsson, Jenny, et al.
(författare)
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Miljöövervakningsprojekt i Södertälje kanalområde för bedömning av effekterna från muddring och tippning av förorenade sediment. Multivariat utvärdering av toxiciteten mot brackvattenorganismer exponerade för sediment från Hallsfjärden - Delrapport 3
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I det kontrollprogram som har följt efter muddringen i Södertälje kanal har analyser gjorts av metaller och PAH i bottenvatten och sediment. Toxiciteten av ämnen i vattenfasen utlösta från sedimenten mot aborryngel, paddyngel, pungräka och dammsnäcka har analyserats. Dessa organismer ger en god bild av effekterna i ekosystemet eftersom de representerar djurgrupperna; fisk, groddjur, kräftdjur och snäckor. För att studera hur föroreningarna har påverkat toxiciteten i området har en multivariat utvärdering gjorts för att hitta eventuella korrelationer mellan toxicitet och föroreningar utlösta i vattenfasen. Datamaterialet baseras på sedimentdata från 5 provtagningspunkter varav 4 provtagningspunkter är belägna i Hallsfjärden, söder om Södertälje, och en referenspunkt i Forsmark, norra Uppland. De uppmätta effekterna på de olika organismerna ger en grov bild av det som lösts ut till vattenfasen från sedimenten. Det begränsade antalet provtagningspunkter innebär att resultaten av den multivariata utvärderingen måste beaktas med viss försiktighet. Resultatet av utvärderingen visade att toxiciteten är störst vid Fläsklösa och vid Halls Holme belägna i Hallsfjärden. Vid Halls Holme är toxiciteten i vattenfasen hög för abboryngel. Fläsklösa ger inte lika entydiga resultat vid jämförelse med Halls Holme. Utvärderingen visade att både utlösta metaller och PAH har en toxisk effekt på de undersökta organismerna. PAH påverkar främst abborryngel. Paddyngel påverkas både av metaller och PAH. Vissa variabler för pungräka påverkas av metaller och andra av PAH medan dammsnäckan inte verkar påverkas nämnvärt av de analyserade föroreningarna.
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