| 1. |
- Arndt, Christoph, et al.
(författare)
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Laser Applications to Chemical, Security, and Environmental Analysis : introduction to the feature issue
- 2023
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Ingår i: Applied Optics. - 1559-128X. ; 62:6, s. 1-3
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Tidskriftsartikel (refereegranskat)abstract
- The eighteenth topical meeting on Laser Applications to Chemical, Security, and Environmental Analysis (LACSEA) was held in Vancouver, Canada from 11–15 July 2022, as part of the Optica Optical Sensors and Sensing Congress in a hybrid format allowing on-site and online attendance. The meeting featured a broad range of distinguished papers focusing on recent advances in laser and optical spectroscopy. A total of 52 contributed and invited papers were presented during the meeting, including topics such as photo-acoustic spectroscopy, imaging, non-linear technologies, frequency combs, remote sensing, environmental monitoring, aerosols, combustion diagnostics, hypersonic flow diagnostics, nuclear diagnostics, fs/ps applications, and machine learning and computational sensing.
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| 2. |
- Borisov, Vladislav, et al.
(författare)
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Tuning skyrmions in B20 compounds by 4d and 5d doping
- 2022
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Ingår i: Physical Review Materials. - : American Physical Society (APS). - 2475-9953. ; 6:8
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Tidskriftsartikel (refereegranskat)abstract
- Skyrmion stabilization in novel magnetic systems with the B20 crystal structure is reported here, primarily based on theoretical results. The focus is on the effect of alloying on the 3d sublattice of the B20 structure by substitution of heavier 4d and 5d elements, with the ambition to tune the spin-orbit coupling and its influence on magnetic interactions. State-of-the-art methods based on density functional theory are used to calculate both isotropic and anisotropic exchange interactions. Significant enhancement of the Dzyaloshinskii-Moriya interaction is reported for 5d-doped FeSi and CoSi, accompanied by a large modification of the spin stiffness and spiralization. Micromagnetic simulations coupled to atomistic spin-dynamics and ab initio magnetic interactions reveal the spin-spiral nature of the magnetic ground state and field-induced skyrmions for all these systems. Especially small skyrmions similar to 50 nm are predicted for Co0.75Os0.25Si, compared to similar to 148 nm for Fe0.75Co0.25Si. Convex-hull analysis suggests that all B20 compounds considered here are structurally stable at elevated temperatures and should be possible to synthesize. This prediction is confirmed experimentally by synthesis and structural analysis of the Ru-doped CoSi systems discussed here, both in powder and in single-crystal forms.
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| 3. |
- Hot, Dina, et al.
(författare)
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Investigation of laser-induced grating spectroscopy of O2 for accurate temperature measurements towards applications in harsh environments
- 2021
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Ingår i: Journal of Raman Spectroscopy. - : Wiley. - 0377-0486 .- 1097-4555. ; 52:9, s. 1569-1581
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Tidskriftsartikel (refereegranskat)abstract
- We present an in-depth investigation of laser-induced grating spectroscopy (LIGS) for temperature measurements in practical applications using a narrow-band dye laser with 760 nm wavelength and a pulse duration of 8 ns as the source for the pump beams creating the laser-induced grating. The pump laser wavelength was set to be either resonant with the (Formula presented.) transition from the (Formula presented.) band of O2 for generation of thermal LIGS or nonresonant for generation of purely electrostrictive LIGS. Signals were generated in ambient air as well as in high-pressure or high-temperature dry air mixtures. Pump laser irradiances up to 11 GW/cm2 were used, which resulted in strong electrostrictive contribution to the overall LIGS signals at atmospheric pressure, with a low thermal contribution due to the weak absorption by the singlet O2 (Formula presented.). The advantage and disadvantage of thermal or electrostrictive LIGS for temperature measurements are discussed, as well as potential applications in high-pressure environments. Furthermore, the precision of the temperature measurement is discussed by comparing different analysis methods.
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| 4. |
- Hot, Dina, et al.
(författare)
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Mid-infrared laser-induced thermal grating spectroscopy of hot water lines for flame thermometry
- 2021
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 38:1, s. 1885-1893
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Tidskriftsartikel (refereegranskat)abstract
- In this work we report the impact of using mid-infrared laser-induced thermal grating spectroscopy (IRLITGS) for temperature measurements in flames by probing hot water lines. The measurements have been performed in the product zone of laminar atmospheric CH 4 /H 2 /air flat flames with equivalence ratio ranging between 0.6 and 1.05. LITGS is a technique based on thermalization through collisions of the excited molecules for generation of a laser-induced grating, which then decays through thermal diffusion. As such, it tends to have limited application in atmospheric flames compared to flame measurements at elevated pressures due to the faster decay at low gas densities. However, by using mid-IR pump laser beams, it enables the generation of laser-induced gratings with large grating spacing, resulting in strong signal intensities and long signal durations. Single-shot IR-LITGS signals were recorded in the different CH 4 /H 2 /air flames that covered a temperature range between 1500 and 1800 K. To test the accuracy, the IR-LITGS flame temperature measurements were compared with laser Rayleigh scattering measurements and the result were in good agreement with each other. The IR-LITGS flame temperature measurements show a repetitive single-shot temperature precision better than 1% and an accuracy of 2.5% of the flame temperature. An IR-LITGS excitation scan of water in the flame shows that some ro-vibrational transitions exhibit no IR-LITGS signal, probably due to less efficient collisional energy transfer mechanism. This is important when deciding the wavelength to use for IR-LITGS flame temperature measurements using water absorption.
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| 5. |
- Pedersen, Rasmus L., et al.
(författare)
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Saturation Dependence of Flame Thermometry by Mid-IR Degenerate Four Wave Mixing
- 2021
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Ingår i: Applied Spectroscopy. - : SAGE Publications. - 0003-7028 .- 1943-3530. ; 75:1, s. 107-114
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Tidskriftsartikel (refereegranskat)abstract
- It has previously been demonstrated that the ratio of the degenerate four wave mixing signal from two hot water line groups near 3231 cm–1 can be used for seedless flame temperature measurements. This paper presents an investigation of the impact of saturation effects on the measured signal intensity from each line group, as well as an estimation of the accuracy of the method. The saturation effects observed here would result in a large systematic error if they are not taken into account when using the degenerate four-wave mixing intensity of these water line groups to calculate the flame temperature.
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| 6. |
- Popova, Gergana, et al.
(författare)
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Optimization of Tetrahydroindazoles as Inhibitors of Human Dihydroorotate Dehydrogenase and Evaluation of Their Activity and In Vitro Metabolic Stability
- 2020
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Ingår i: Journal of Medicinal Chemistry. - : American Chemical Society (ACS). - 0022-2623 .- 1520-4804. ; 63:8, s. 3915-3934
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Tidskriftsartikel (refereegranskat)abstract
- Human dihydroorotate dehydrogenase (DHODH), an enzyme in the de novo pyrimidine synthesis pathway, is a target for the treatment of rheumatoid arthritis and multiple sclerosis and is re-emerging as an attractive target for cancer therapy. Here we describe the optimization of recently identified tetrahydroindazoles (HZ) as DHODH inhibitors. Several of the HZ analogues synthesized in this study are highly potent inhibitors of DHODH in an enzymatic assay, while also inhibiting cancer cell growth and viability and activating p53-dependent transcription factor activity in a reporter cell assay. Furthermore, we demonstrate the specificity of the compounds toward the de novo pyrimidine synthesis pathway through supplementation with an excess of uridine. We also show that induction of the DNA damage marker gamma-H2AX after DHODH inhibition is preventable by cotreatment with the pancaspase inhibitor Z-VAD-FMK. Additional solubility and in vitro m etabolic stability profiling revealed compound 51 as a favorable candidate for preclinical efficacy studies.
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| 7. |
- Ruchkina, Maria, et al.
(författare)
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Laser-induced thermal grating spectroscopy based on femtosecond laser multi-photon absorption
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Laser-induced grating spectroscopy (LIGS) is for the first time explored in a configuration based on the crossing of two focused femtosecond (fs) laser pulses (800-nm wavelength) and a focused continuous-wave (cw) laser beam (532-nm wavelength). A thermal grating was formed by multi-photon absorption of the fs-laser pulses by N 2 with a pulse energy around 700 μ J (∼ 45 TW/cm 2). The feasibility of this LIGS configuration was investigated for thermometry in heated nitrogen gas flows. The temperature was varied from room temperature up to 750 K, producing strong single-shot LIGS signals. A model based on the solution of the linearized hydrodynamic equations was used to extract temperature information from single-shot experimental data, and the results show excellent agreement with the thermocouple measurements. Furthermore, the fluorescence produced by the fs-laser pulses was investigated. This study indicates an 8-photon absorption pathway for N 2 in order to reach the B 3Π g state from the ground state, and 8 + 5 photon excitation to reach the B2Σu+ state of the N2+ ion. At pulse energies higher than 1 mJ, the LIGS signal was disturbed due to the generation of plasma. Additionally, measurements in argon gas and air were performed, where the LIGS signal for argon shows lower intensity compared to air and N 2.
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| 8. |
- Sahlberg, Anna, et al.
(författare)
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Don't extinguish my fire – Understanding public resistance to a Swedish policy aimed at reducing particle emissions by phasing out old wood stoves
- 2022
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Ingår i: Energy Policy. - : Elsevier Ltd. - 0301-4215 .- 1873-6777. ; 167
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Tidskriftsartikel (refereegranskat)abstract
- Wood stoves emit particulate matter when used for domestic heating. Consequently, the National Board of Housing, Building and Planning in Sweden enforced a prohibition of new installations of old wood stoves in 2017 to protect the public health. The prohibition caused a public backlash that organized itself as a “wood stove rising”, eventually leading to a cancellation of the new legislation in 2019. We performed comprehensive interviews with 11 signatories of the original appeal to analyze the underlying motives for combating the implementation of this pro-environmental energy policy. We find that domestic heating through fire-making is an age-old human behavior that is deeply connected to several social and emotional human needs, but also to survival in remote areas with cold climate. The likelihood of policy observance and acceptance is higher if the policy is not perceived as being in direct conflict with these needs: basic emotion regulation, sensations of tradition and connection to other people, and means of crisis management for the individual. We also find that the protesters acted out of a sustainability perspective, albeit one where the continued use of functional devices was valued more than the perceived wear-and-tear of replacing outdated technology. © 2022 The Authors
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| 9. |
- Sahlberg, Anna-Lena, et al.
(författare)
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Gas in Scattering Media Absorption Spectroscopy on Small and Large Scales: Towards the Extension of Lung Spectroscopic Monitoring to Adults
- 2021
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Ingår i: Translational Biophotonics. - : Wiley. - 2627-1850.
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Tidskriftsartikel (refereegranskat)abstract
- Numerous natural materials are porous, contain free gas, and are scattering light strongly. Scattering brings about a strong trapping of light and an associated prolonged transit time for photons through a medium. In contrast to the matrix materials, gas enclosures require very narrow‐band laser radiation for probing. We have in the present study used the gas in scattering media absorption spectroscopy (GASMAS) method to study free oxygen in thin (cm) samples utilizing a tunable diode laser, while a pulsed dye laser was employed in corresponding measurements on larger samples, up to the meter scale. Time‐resolved spectroscopy was in both cases used to assess the temporal distribution of the detected photons, mapping the path lengths through the media, which ranged between few centimeters up to 100 m. This study explores the feasibility to extend recent successful monitoring of gases in neonatal infant lungs to the case of larger children or even adults, which could have very important applications, for example, in ventilator setting optimization for severely ill patients, suffering, for example, from SARS‐CoV‐2. The conclusion of our work is that this goal most realistically can be reached by applying intra‐tracheal laser light illumination at the 1 W power level, employing a tapered amplifier, injected with a distributed feed‐back diode‐laser oscillator output and combined with wavelength‐modulation spectroscopy.
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| 10. |
- Sahlberg, Anna Lena, et al.
(författare)
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Mid-Infrared Generated Laser-Induced Grating Signals in Methane-Containing Gas Mixtures as Indicators of Composition, Pressure, and Temperature
- 2024
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Ingår i: Applied Spectroscopy. - 0003-7028. ; 78:4
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Tidskriftsartikel (refereegranskat)abstract
- The present work is aimed at studying how spatially periodic modulations of the refractive index of the medium, i.e., laser-induced gratings (LIGs), generated in a gas mixture containing methane (CH4) by nanosecond pulses of resonant mid-infrared laser radiation, can be used to measure various gas parameters. It is investigated to what extent the temporal profiles of the LIG signals, recorded as the power of the diffracted by LIGs continuous wave probe radiation, are specific to the composition, pressure, and temperature of a selected buffer gas. This specificity is illustrated by the LIG signal profiles recorded in the experiments in different gas mixtures under various conditions. Experimental data show that large LIG signals can be obtained even in mixtures with CH4 concentrations as low as ∼100 parts per million due to the strong absorption of the excitation light and subsequent rapid, highly exothermic, and partner-dependent collisional energy exchange of the laser-excited molecules with the environment. These two factors ensure high LIG generation efficiency by a small number of CH4 molecules and high sensitivity of signal strength and profile to variations of gas parameters.
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