| 1. |
- Afzelius, Mikael, et al.
(författare)
-
Pure rotational coherent anti-Stokes Raman spectroscopy in mixtures of CO and N-2
- 2004
-
Ingår i: Applied Optics. - 2155-3165. ; 43:36, s. 6664-6672
-
Tidskriftsartikel (refereegranskat)abstract
- We present a model for quantitative measurements in binary mixtures of nitrogen and carbon monoxide by the use of dual-broadband rotational coherent anti-Stokes Raman spectroscopy. The model has been compared with experimental rotational coherent anti-Stokes Raman scattering spectra recorded within the temperature range of 294-702 K. Temperatures and concentrations were evaluated by spectral fits using libraries of theoretically calculated spectra. The relative error of the temperature measurements was 1-2%, and the absolute error of the CO concentration measurements was <0.5% for temperatures less than or equal to600 K. For higher temperatures, the gas composition was not chemically stable, and we observed a conversion of CO to CO2. The influence of important spectroscopic parameters such as the anisotropic polarizability and Raman line-broadening coefficients are discussed in terms of concentration measurements. In particular, it is shown that the CO concentration measurement was more accurate if N-2-CO and CO-N-2 line-broadening coefficients were included in the calculation. The applicability of the model for quantitative flame measurements is demonstrated by measuring CO concentrations in ethylene/air flames. (C) 2004 Optical Society of America.
|
|
| 2. |
- Blom, Carin, et al.
(författare)
-
Den osynliga värdeskaparens framtid
- 2011
-
Ingår i: Ekonomiska samfundets tidskrift. - Helsingfors : Ekonomiska Samfundet i Finland. - 0013-3183 .- 2323-1378. ; :3, s. 157-168
-
Tidskriftsartikel (refereegranskat)abstract
- Hos gemene man anses partihandel ofta vara detsamma som ledet mellan producent och detaljhandlare. Partihandeln är emellertid betydligt mer komplex än så. Partihandeln består av flera olika delbranscher som kan vara mycket olika varandra. En del partihandelsbranscher ligger närmare detaljhandeln, medan andra har mycket gemensamt med tillverkningsindustrin. I denna artikel presenteras statstik över den Svenska partihandelns betydelse i ekonomin, dess geografiska spridning illustreras grafiskt, och slutligen genomförs tre fallstudier av Svenska partihandelsföretag. I de tre fallstudierna anges några faktorer ha större betydelse än andra för partihandlarnas framtid. Dessa faktorer, som diskuteras utförligt i artikeln, är bland annat teknologisk utveckling, internationalisering, och en förändrad konkurrenssituation.
|
|
| 3. |
- Bohlin, Alexis, et al.
(författare)
-
Improvement of rotational CARS thermometry in fuel-rich hydrocarbon flames by inclusion of N-2-H-2 Raman line widths
- 2009
-
Ingår i: Journal Of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 40:7, s. 788-794
-
Konferensbidrag (refereegranskat)abstract
- In rotational coherent anti-Stokes Raman spectroscopy (CARS) thermometry applied to air-fed flames, the temperature sensitivity mainly depends on the intensity distribution of the nitrogen spectral lines. Temperatures are estimated by numerical fitting of theoretical spectra to experimental ones, and one uncertainty in the calculation of theoretical CARS spectra for specific flame conditions is the accuracy in utilized line-broadening coefficients. In a previous article, self-broadened N-2-N-2 line widths were considered in the spectral calculations as well as those of N-2-CO, N-2-CO2, N-2-H2O, and N-2-O-2- In the present article, we also include N-2-H-2 line widths calculated from a newly developed model, and it is shown that the evaluated temperature from flame spectra increases with increasing mole fractions of hydrogen. For example, in a very rich flame at Phi = 2.5, the use of available line-width data for all major species gives a temperature raise of 72 K at a temperature of similar to 1700 K, in comparison with using self-broadened N-2-N-2 line widths only. Half of this temperature raise is related to the inclusion of N-2-H-2 line widths. This article emphasizes the importance of using adequate line-broadening models for rotational CARS thermometry in flames. Copyright (C) 2009 John Wiley & Sons, Ltd.
|
|
| 4. |
- Bohlin, Alexis, et al.
(författare)
-
Rotational CARS N-2 thermometry: validation experiments for the influence of nitrogen spectral line broadening by hydrogen
- 2010
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486. ; 41:8, s. 875-881
-
Konferensbidrag (refereegranskat)abstract
- Rotational coherent anti-Stokes Raman spectroscopy (CARS) in fuel-rich hydrocarbon flames, with a large content of hydrogen in the product gases (similar to 20%), has in previous work shown that evaluated temperatures are raised several tens of Kelvin by taking newly derived N-2-H-2 Raman line widths into account. To validate these results, in this work calibrated temperature measurements at around 300, 500 and 700 K were performed in a cell with binary gas mixtures of nitrogen and hydrogen. The temperature evaluation was made with respect to Raman line widths either from self-broadened nitrogen only, N-2-N-2 [energy-corrected-sudden (ECS)], or by also taking nitrogen broadened by hydrogen, N-2-H-2 [Robert-Bonamy (RB)], Raman line widths into account. With increased amount of hydrogen in the cell at constant temperature, the evaluated CARS temperatures were clearly lowered with the use of Raman line widths from self-broadened nitrogen only, and the case with inclusion of N-2-H-2 Raman line widths was more successful. The difference in evaluated temperatures between the two different sets increases approximately linearly, reaching 20 K (at T similar to 300 K), 43 K (at T = 500 K) and 61 K (at T = 700 K) at the highest hydrogen concentration (90%). The results from this work further emphasize the importance of using adequate Raman line widths for accurate rotational CARS thermometry. Copyright (C) 2010 John Wiley & Sons, Ltd.
|
|
| 5. |
- Buldyreva, J, et al.
(författare)
-
Linewidth modelling of C2H2-N-2 mixtures tested by rotational CARS measurements
- 2006
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 37:6, s. 647-654
-
Tidskriftsartikel (refereegranskat)abstract
- The acetylene-nitrogen system is investigated in a combined theoretical and experimental effort in view of its thermometry applications. Accurate values of the rotational Raman linewidths of acetylene are of crucial importance for the computation of spectra from rotational coherent anti-Stokes Raman scattering (CARS) used for temperature and concentration evaluations. Since the direct measurements of these linewidths are not available, they are rigorously calculated by a semi-classical Robert-Bonamy formalism employing exact trajectories. The computed linewidths are used as input parameters in the theoretical spectra simulation, which is also improved by the inclusion of an interbranch interference with coherent Stokes Raman scattering (CSRS). These theoretical spectra are used to evaluate the temperature from experimental CARS spectra of acetylene-nitrogen mixtures recorded in the pressure range 0.1-0.6 MPa. The new linewidths (NLWs) and the CSRS interference inclusion result in a clear improvement of spectral fitting as well as in reasonable values of evaluated temperatures. Copyright (c) 2006 John Wiley & Sons, Ltd.
|
|
| 6. |
- Feigenwinter, Christian, et al.
(författare)
-
Comparison of horizontal and vertical advective CO2 fluxes at three forest sites
- 2008
-
Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 1873-2240 .- 0168-1923. ; 148:1, s. 12-24
-
Tidskriftsartikel (refereegranskat)abstract
- Extensive field measurements have been performed at three CarboEurope-Integrated Project forest sites with different topography (Renon/Ritten, Italian Alps, Italy; Wetzstein, Thuringia, Germany; Norunda, Uppland, Sweden) to evaluate the relevant terms of the carbon balance by measuring CO2 concentrations [CO2] and the wind field in a 3D multi-tower cube setup. The same experimental setup (geometry and instrumentation) and the same methodology were applied to all the three experiments. It is shown that all sites are affected by advection in different ways and strengths. Everywhere, vertical advection (F-VA) occurred only at night. During the day, F-VA disappeared because of turbulent mixing, leading to a uniform vertical profile of [CO2]. Mean F-VA was nearly zero at the hilly site (wetzstein) and at the flat site (Norunda). However, large, momentary positive or negative contributions occurred at the flat site, whereas vertical non-turbulent fluxes were generally very small at the hilly site. At the slope site (Renon), F-VA was always positive at night because of the permanently negative mean vertical wind component resulting from downslope winds. Horizontal advection also occurred mainly at night. It was positive at the slope site and negative at the flat site in the mean diurnal course. The size of the averaged non-turbulent advective fluxes was of the same order of magnitude as the turbulent flux measured by eddy-covariance technique, but the scatter was very high. This implies that it is not advisable to use directly measured quantities of the non-turbulent advective fluxes for the estimation of net ecosystem exchange (NEE) on e.g. an hourly basis. However, situations with and without advection were closely related to local or synoptic meteorological conditions. Thus, it is possible to separate advection affected NEE estimates from fluxes which are representative of the source term. However, the development of a robust correction scheme for advection requires a more detailed site-specific analysis of single events for the identification of the relevant processes. This paper presents mean characteristics of the advective CO2 fluxes in a first site-to-site comparison and evaluates the main problems for future research.
|
|
| 7. |
- Lindroth, Anders, et al.
(författare)
-
Effects of low thinning on carbon dioxide fluxes in a mixed hemiboreal forest
- 2018
-
Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923. ; 262, s. 59-70
-
Tidskriftsartikel (refereegranskat)abstract
- We used eddy-covariance (EC) measurements of net ecosystem exchange (NEE) above canopy to assess the effects of thinning on CO2 fluxes at the ICOS Sweden site Norunda in central Sweden. This forest site consists of mixed pine and spruce stands approx. 100 years old. The thinning during late autumn 2008, performed in a semi-circle from the mast extending 200 m outwards harvested about 25% of the volume. Measurements were conducted from 2007 to 2016 and thus, above canopy fluxes were recorded two years before and eight years after the thinning. We also measured the net flux from the forest floor with automatic chambers in three locations and with below-canopy EC during shorter periods before and after thinning. The chamber measurements during the first part of the growing season after thinning showed strongly enhanced effluxes in the order of 150–250% of the pre-thinning values. These chamber measurements were made on drier places within the thinned area because waterlogging made it impossible to use chambers at all available locations. The below-canopy EC measurements, which had a larger footprint as compared to the chambers, showed less enhanced fluxes (in the order of 35%). This footprint included also wetter areas. The above canopy EC measurements showed a reduction of daytime net flux by approx. 30% during the first summer after thinning. The median growing season fluxes then slowly increased but were not restored to the pre-thinning levels eight years after thinning. There was also a small decrease in growing season ecosystem respiration during the first summer after thinning and with a continued decreasing trend over time. It was concluded that this decrease in respiration was caused by successively decreasing decomposition of coarse organic substrates resulting from the thinning. This respiration decrease over time persisted even under gradual biomass increase, which otherwise would indicate increasing autotrophic respiration. The light-response and respiration models fitted to all data did not show any trends in daytime or nighttime fluxes so the conclusion was that the trends were caused by the thinning and not because of trends in meteorological drivers. The annual values contrasted with the summertime results since only a minor effect was observed on the annual NEE. Both ecosystem respiration and gross primary productivity were reduced as an effect of thinning. We explained the different summertime versus annual effects to be caused by the decrease in ecosystem respiration since respiration is dominating the NEE during non-growing season periods when photosynthesis is very low or even zero. Our results are a strong indication that the NEE of a forest could be maintained over time with harvesting practices that avoids clear-cutting and thereby enhance the total carbon uptake of forests.
|
|
| 8. |
- Tegel, Hanna, et al.
(författare)
-
High throughput generation of a resource of the human secretome in mammalian cells
- 2020
-
Ingår i: New Biotechnology. - : Elsevier BV. - 1871-6784 .- 1876-4347. ; 58, s. 45-54
-
Tidskriftsartikel (refereegranskat)abstract
- The proteins secreted by human tissues and blood cells, the secretome, are important both for the basic understanding of human biology and for identification of potential targets for future diagnosis and therapy. Here, a high-throughput mammalian cell factory is presented that was established to create a resource of recombinant full-length proteins covering the majority of those annotated as 'secreted' in humans. The full-length DNA sequences of each of the predicted secreted proteins were generated by gene synthesis, the constructs were transfected into Chinese hamster ovary (CHO) cells and the recombinant proteins were produced, purified and analyzed. Almost 1,300 proteins were successfully generated and proteins predicted to be secreted into the blood were produced with a success rate of 65%, while the success rates for the other categories of secreted proteins were somewhat lower giving an overall one-pass success rate of ca. 58%. The proteins were used to generate targeted proteomics assays and several of the proteins were shown to be active in a phenotypic assay involving pancreatic beta-cell dedifferentiation. Many of the proteins that failed during production in CHO cells could be rescued in human embryonic kidney (HEK 293) cells suggesting that a cell factory of human origin can be an attractive alternative for production in mammalian cells. In conclusion, a high-throughput protein production and purification system has been successfully established to create a unique resource of the human secretome.
|
|
| 9. |
- Vestin, Erika, et al.
(författare)
-
Herpes simplex viral infection doubles the risk of dementia in a contemporary cohort of older adults : a prospective study
- 2024
-
Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 97:4, s. 1841-1850
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Evidence indicates that herpes simplex virus (HSV) participates in the pathogenesis of Alzheimer’s disease (AD).Objective: We investigated AD and dementia risks according to the presence of herpesvirus antibodies in relation to anti-herpesvirus treatment and potential APOE ε4 carriership interaction.Methods: This study was conducted with 1002 dementia-free 70-year-olds living in Sweden in 2001–2005 who were followed for 15 years. Serum samples were analyzed to detect anti-HSV and anti-HSV-1 immunoglobulin (Ig) G, anti-cytomegalovirus (CMV) IgG, anti-HSV IgM, and anti-HSV and anti-CMV IgG levels. Diagnoses and drug prescriptions were collected from medical records. Cox proportional-hazards regression models were applied.Results: Cumulative AD and all-cause dementia incidences were 4% and 7%, respectively. Eighty-two percent of participants were anti-HSV IgG carriers, of whom 6% received anti-herpesvirus treatment. Anti-HSV IgG was associated with a more than doubled dementia risk (fully adjusted hazard ratio = 2.26, p = 0.031). No significant association was found with AD, but the hazard ratio was of the same magnitude as for dementia. Anti-HSV IgM and anti-CMV IgG prevalence, anti-herpesvirus treatment, and anti-HSV and -CMV IgG levels were not associated with AD or dementia, nor were interactions between anti-HSV IgG and APOE ε4 or anti-CMV IgG. Similar results were obtained for HSV-1.Conclusions: HSV (but not CMV) infection may be indicative of doubled dementia risk. The low AD incidence in this cohort may have impaired the statistical power to detect associations with AD.
|
|
| 10. |
- Vestin, Erika, et al.
(författare)
-
Herpes Simplex Viral Infection Doubles the Risk of Dementia in a Contemporary Cohort of Older Adults : A Prospective Study
- 2024
-
Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 97:4, s. 1841-1850
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Evidence indicates that herpes simplex virus (HSV) participates in the pathogenesis of Alzheimer's disease (AD). Objective: We investigated AD and dementia risks according to the presence of herpesvirus antibodies in relation to antiherpesvirus treatment and potential APOE epsilon 4 carriership interaction. Methods: This studywas conducted with 1002 dementia-free 70-year-olds living in Sweden in 2001-2005 who were followed for 15 years. Serum samples were analyzed to detect anti-HSV and anti-HSV-1 immunoglobulin (Ig) G, anti-cytomegalovirus (CMV) IgG, anti-HSV IgM, and anti-HSV and anti-CMV IgG levels. Diagnoses and drug prescriptions were collected from medical records. Cox proportional-hazards regression models were applied. Results: CumulativeADand all-cause dementia incidences were 4% and 7%, respectively. Eighty-two percent of participants were anti-HSV IgG carriers, of whom 6% received anti-herpesvirus treatment. Anti-HSV IgG was associated with a more than doubled dementia risk (fully adjusted hazard ratio = 2.26, p = 0.031). No significant association was found with AD, but the hazard ratio was of the same magnitude as for dementia. Anti-HSV IgM and anti-CMV IgG prevalence, anti-herpesvirus treatment, and anti-HSV and -CMV IgG levels were not associated with AD or dementia, nor were interactions between anti-HSV IgG and APOE epsilon 4 or anti-CMV IgG. Similar results were obtained for HSV-1. Conclusions: HSV (but not CMV) infection may be indicative of doubled dementia risk. The low AD incidence in this cohort may have impaired the statistical power to detect associations with AD.
|
|
| 11. |
- Vestin, Fredrik
(författare)
-
Development of dual-broadband rotational CARS for applied flame diagnostics
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis work involved the further development of the dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) approach to applied flame diagnostics. This included the development of new experimental approaches, of new theoretical rotational CARS models, and of new evaluation routines as well as exploration of the potential of DB-RCARS to provide reliable thermometric measurements and measurements of concentration under a variety of conditions common in combustion research. A polarization approach for rotational CARS was developed, one shown to completely suppress the non-resonant contribution of the CARS signal. Use of it was demonstrated by thermometry on the fuel side of a laminar methane diffusion flame. Use of DB-RCARS, together with a modeless dye laser that was constructed was also demonstrated. It was shown that under ambient conditions the temperature precision was significantly improved. Rotational CARS models for carbon dioxide and acetylene were developed and improved, respectively. This was done in connection with experiments under well defined conditions aimed at validating the use of these models for thermometry and measurements of concentration. Also, simultaneous multi-species detection (of N2, O2, CO2 and CO) and thermometry were demonstrated by means of rotational CARS in a laminar carbon monoxide diffusion flame. A species-specific weighting routine was developed that enhances importance of weak peaks in the spectral fitting algorithm. Use of the routine was found to improve the precision and the accuracy of measurements of concentration. The routine was applied to evaluation of low concentrations of O2 and CO in spectra recorded in laminar premixed hydrocarbon flames. The routine also improved the temperature precision of high temperature measurements. Thermometry was applied to the product gas of laminar premixed hydrocarbon flames. The effects of collisional broadening on the rotational Raman linewidths of nitrogen brought about by the product gas species involved were shown to be important in quantitative thermometry. Use of single-shot thermometry in high-pressure hydrocarbon flames was also demonstrated. A prerequisite for quantitative measurements was the calibration measurements in air, N2 and O2 under high temperature and pressure conditions in a cell.
|
|
| 12. |
- Vestin, Fredrik, et al.
(författare)
-
Development of rotational CARS for combustion diagnostics using a polarization approach
- 2007
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1873-2704 .- 1540-7489. ; 31 I, s. 833-840
-
Konferensbidrag (refereegranskat)abstract
- Rotational Coherent anti-Stokes Raman spectroscopy (CARS) has the last decades been developed into a useful tool for thermometry and concentration measurements in combustion. In this paper, we present a novel polarization approach of the technique, which will enhance its potential and widen the range of conditions at which it can be utilized. The theory of the polarization approach is described in detail. It is shown that by specific arrangement of the polarizations of the laser beams, total suppression of the non-resonant background signal can be obtained, and thus by probing only the resonant CARS signal the diagnostic utility of the technique increases. The main benefit of the approach is in situations where the non-resonant background signal is relatively high in comparison with the resonant signal. The high potential of polarization rotational CARS for thermometry is demonstrated in some illustrative examples, for example, nitrogen thermometry on the fuel side of diffusion flames, and carbon monoxide thermometry in the product gas of ethylene/oxygen/argon-flames. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
|
|
| 13. |
- Vestin, Fredrik, et al.
(författare)
-
Dual-broadband rotational CARS thermometry in the product gas of hydrocarbon flames
- 2005
-
Ingår i: Symposium (International) on Combustion. - : Elsevier BV. - 0082-0784. ; 30:1, s. 1673-1680
-
Tidskriftsartikel (refereegranskat)abstract
- Coherent anti-Stokes Raman spectroscopy (CARS) is an established technique for gas-phase thermometry in combustion. In this work, rotational CARS in the dual-broadband approach has been investigated for flame thermometry in the product gas of ethylene/air flames in a wide range of equivalence ratios (0.5 < phi < 2.5). The nitrogen lines dominated the rotational CARS spectra in the whole equivalence range, but for fuel-lean flames also oxygen lines gave significant spectral contributions. Therefore, the temperature evaluation was based on spectral fitting of both nitrogen and oxygen. Product gas species such as carbon dioxide, water, carbon monoxide, and hydrogen contribute to the non-resonant susceptibility of the gas and influence the nitrogen and oxygen linewidths through collisions. In this work, the main focus was on the influence of these collisions on the nitrogen and oxygen Raman linewidths and consequently the evaluated temperature in the product gas of flames. In the range of studied equivalence ratios with various amounts of different product gas species, the evaluated temperature was raised up to 45 K when including broadening from CO2, H2O, and CO on the measured nitrogen and oxygen lines. It was also concluded that H2O was the main contributor in all non-sooting flames. The influence of the non-resonant susceptibility in the spectral evaluation is discussed, and its coupling to the inclusion of the line broadening from product gas species as well. It has thus been shown that line-broadening effects from product gas species are highly important for quantitative rotational CARS thermometry in flames. (c) 2004 The Combustion Institute.
|
|
| 14. |
- Vestin, Fredrik, et al.
(författare)
-
Improved species concentration measurements using a species-specific weighting procedure on rotational CARS spectra
- 2005
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 36:2, s. 95-101
-
Tidskriftsartikel (refereegranskat)abstract
- Rotational coherent anti-Stokes Raman spectroscopy (CARS) is used for measurements of temperatures and relative species concentrations. The evaluation of a rotational CARS spectrum is normally performed using a least-squares fitting algorithm to find the best-fit theoretical spectrum in a library of spectra calculated at different temperatures and relative concentrations. A general problem is that species with weak spectral features have a minor influence on the results in the standard evaluation procedure. A species-specific weighting (SSW) procedure enhancing the influence of weak spectral features in the spectral fitting algorithm has therefore been developed. The SSW procedure was tested on the evaluation of low concentrations Of 02 in mixtures with N-2, and it is shown that both the accuracy and precision of single-shot spectra concentration measurements are improved by use of the SSW evaluation procedure. Also, a comparison with previously used weighting procedures shows that this approach is superior. The application of the technique to oxygen concentration measurements in the product gas of a fuel-lean flame is demonstrated. In addition, a test was made using the developed weighting procedure for thermometry, by applying spectral weighting to the rotational spectrum originating from the first thermally excited vibrational state. The precision of the temperature measurements was then slightly improved.
|
|
| 15. |
- Vestin, Fredrik, et al.
(författare)
-
Improved temperature precision in rotational coherent anti-Stokes Raman spectroscopy with a modeless dye laser
- 2006
-
Ingår i: Applied Optics. - 2155-3165. ; 45:4, s. 744-747
-
Tidskriftsartikel (refereegranskat)abstract
- Single-shot thermometry with dual-broadband rotational coherent anti-Stokes Raman spectroscopy that employs amplified spontaneous emission from a broadband modeless dye laser has been examined. Evaluation of single-shot spectra of air, N-2, and O-2 showed an improved temperature precision at room temperature compared with the precision obtained with a conventional dye laser. A comparison was also made between the use of single-mode and multimode Nd:YAG lasers as sources for narrowband radiation, and in all cases the single-mode Nd:YAG laser resulted in higher precision. The experimental results are compared with theoretical predictions. (c) 2006 Optical Society of America.
|
|
| 16. |
- Vestin, Fredrik, et al.
(författare)
-
Laser-induced breakdown spectroscopy applied on low-alloyed zinc samples
- 2010
-
Konferensbidrag (refereegranskat)abstract
- The use of laser-induced breakdown spectroscopy for chemical analysis in the single-shot regime has been investigated for low-alloyed zinc samples. Several parameters that are important for plasma formation has been investigated and their importance for accurate and precise single-shot measurements are discussed. The standard deviation is compared for measurements performed on a day-to-day basis during four days and for a measurement series consisting of five measurements in one day. It was found that the spread is not larger for a measurement series performed on a single day compared to day-to-day basis. The influence of local spatial inhomogeneities of the alloy elements in the sample concentrations is discussed in this context and the reference samples have been investigated with a scanning electron microscopy and light optical microscopy to verify this. It is found that the relative standard deviation of the signal depends to large extent on the sample homogeneity at low concentrations. The importance of spatial averaging for LIBS when doing calibrations is established in this case. The relative error for single-shot measurements will depend on the slope of the analytical curve and increase at lower concentrations. © 2010 Elsevier Ltd. All rights reserved.
|
|
| 17. |
- Vestin, Fredrik, et al.
(författare)
-
Rotational CARS for simultaneous measurements of temperature and concentrations of N-2, O-2, CO, and CO2 demonstrated in a CO/air diffusion flame
- 2009
-
Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 32, s. 847-854
-
Tidskriftsartikel (refereegranskat)abstract
- Rotational coherent anti-Stokes Raman spectroscopy (CARS) has over the years demonstrated its strong potential to measure temperature and relative concentrations of major species in combustion. A recent work is the development and experimental validation of a CO2 model for thermometry, in addition to our previous rotational CARS models for other molecules. In the,present work, additional calibration measurements for relative CO2/N-2 concentrations have been made in the temperature range 294-1246 K in standardized CO2/N-2 mixtures. Following these calibration measurements, rotational CARS measurements were performed in a laminar CO/air diffusion flame stabilized on a Wolfhard-Parker burner. High-quality spectra were recorded from the fuel-rich region to the surrounding hot air in a lateral cross section of the flame. The spectra were evaluated to obtain simultaneous profiles of temperature and concentrations of all major species; N-2, O-2, CO, and CO2. The potential for rotational CARS as a multi-species detection technique is discussed in relation to corresponding strategies for vibrational CARS, (c) 2009 The Combustion institute. Published by Elsevier Inc. All rights reserved.
|
|
| 18. |
- Vestin, Fredrik, et al.
(författare)
-
Rotational CARS thermometry at high temperature (1800 K) and high pressure (0.1-1.55 MPa)
- 2007
-
Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 1097-4555 .- 0377-0486. ; 38:8, s. 963-968
-
Tidskriftsartikel (refereegranskat)abstract
- Dual-broadband rotational CARS (DB-RCARS) thermometry has been investigated at high temperature and high pressure. Single-shot measurements were performed at 1800 K, in air and nitrogen at pressures up to 1.55 MPa and in oxygen at pressures up to 0.5 MPa. For all conditions, the resonant signal contribution to the spectra clearly dominated over the non-resonant one, implying the high potential for DB-RCARS for temperature and concentration measurements also at the high temperatures and pressures used in the present investigation. The relative standard deviation was generally similar to 2% for single-shot data at pressures from 0.5 to 1.55 MPa. At the investigated temperature, 1800 K, rotational lines from thermally excited vibrational states could be observed in the highly resolved experimental spectra. Using a previously developed weighting procedure applied to these lines, it was demonstrated that the temperature standard deviation could be lowered with as much as 30%.
|
|
| 19. |
- Vestin, Fredrik, et al.
(författare)
-
Rotational coherent anti-Stokes Raman spectroscopy (CARS) applied to thermometry in high-pressure hydrocarbon flames
- 2008
-
Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 154:1-2, s. 143-152
-
Tidskriftsartikel (refereegranskat)abstract
- Dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) has been investigated for thermometry under high-pressure and high-temperature conditions, in the product gas of fuel-lean hydrocarbon flames up to 1 MPa. Initial calibration measurements made in nitrogen, oxygen, and air, at pressures up to 1.55 MPa and temperatures up to 1800 K, showed good agreement between experimental and theoretical spectra. In the high-pressure flames, high-quality single-shot spectra were recorded in which nitrogen lines dominated, and peaks from CO2 and O-2 were also visible. A spectral model including the species N-2, CO2, and O-2, as well as the best available Raman linewidth models for flame thermometry, were used to evaluate the experimental spectra. Experimental problems as well as considerations related to the spectral evaluation are discussed. This work demonstrates the significant potential of DB-RCARS thermometry for applications in high-pressure and high-temperature environments.
|
|
| 20. |
- Vestin, Fredrik, et al.
(författare)
-
Validation of a rotational coherent anti-Stokes Raman spectroscopy model for carbon dioxide using high-resolution detection in the temperature range 294-1143 K
- 2008
-
Ingår i: Applied Optics. - 2155-3165. ; 47:11, s. 1893-1901
-
Tidskriftsartikel (refereegranskat)abstract
- Experiments were performed in the temperature range of 294 - 1143 K in pure CO2 using high-resolution rotational coherent anti-Stokes Raman spectroscopy (CARS), in the dual-broadband approach. Experimental single-shot spectra were recorded with high spectral resolution using a single-mode Nd:YAG laser and a relay imaging lens system on the exit of a 1 m spectrometer. A theoretical rotational CARS model for CO, was developed for evaluation of the experimental spectra. The evaluated mean temperatures of the recorded single-shot dual-broadband rotational coherent anti-Stokes Raman spectroscopy (DB-RCARS) spectra using this model showed good agreement with thermocouple temperatures, and the relative standard deviation of evaluated single-shot temperatures was generally 2 - 3%. Simultaneous thermometry and relative CO2/N-2-concentration measurements were demonstrated in the product gas of premixed laminar CO/air flames at atmospheric pressure. Although the model proved to be accurate for thermometry up to 1143 K, limitations were observed at flame temperatures where temperatures were overestimated and relative CO2/N-2 concentrations were underestimated. Potential sources for these discrepancies are discussed.
|
|
| 21. |
|
|
