48 results on '"Andreas Ehn"'
Search Results
2. Snapshot multicolor fluorescence imaging using double multiplexing of excitation and emission on a single detector
- Author
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Karolina Dorozynska, Elias Kristensson, Andreas Ehn, Vassily Kornienko, Alexandra Andersson, David Andersson, and Simon Ek
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Fluorescence-lifetime imaging microscopy ,Science ,Multispectral image ,01 natural sciences ,Multiplexing ,Signal ,Article ,010309 optics ,03 medical and health sciences ,Optics ,0103 physical sciences ,Fluorescence spectroscopy ,030304 developmental biology ,Physics ,0303 health sciences ,Multidisciplinary ,business.industry ,Detector ,Imaging and sensing ,Wavelength ,Spectral sensitivity ,Medicine ,business ,Excitation - Abstract
Fluorescence-based multispectral imaging of rapidly moving or dynamic samples requires both fast two-dimensional data acquisition as well as sufficient spectral sensitivity for species separation. As the number of fluorophores in the experiment increases, meeting both these requirements becomes technically challenging. Although several solutions for fast imaging of multiple fluorophores exist, they all have one main restriction; they rely solely on spectrally resolving either the excitation- or the emission characteristics of the fluorophores. This inability directly limits how many fluorophores existing methods can simultaneously distinguish. Here we present a snapshot multispectral imaging approach that not only senses the excitation and emission characteristics of the probed fluorophores but also all cross term combinations of excitation and emission. To the best of the authors’ knowledge, this is the only snapshot multispectral imaging method that has this ability, allowing us to even sense and differentiate between light of equal wavelengths emitted from the same fluorescing species but where the signal components stem from different excitation sources. The current implementation of the technique allows us to simultaneously gather 24 different spectral images on a single detector, from which we demonstrate the ability to visualize and distinguish up to nine fluorophores within the visible wavelength range.
- Published
- 2021
3. Single-shot, spatially-resolved stand-off detection of atomic hydrogen via backward lasing in flames
- Author
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Pengji Ding, Joakim Bood, Marcus Aldén, Maria Ruchkina, and Andreas Ehn
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Materials science ,Hydrogen ,Atom and Molecular Physics and Optics ,General Chemical Engineering ,Physics::Optics ,chemistry.chemical_element ,Energy Engineering ,Ultrashort nonlinear optics ,01 natural sciences ,7. Clean energy ,Signal ,Combustion diagnostics ,law.invention ,010309 optics ,Hydrogen atom ,Optics ,law ,Multiphoton processes ,0103 physical sciences ,Backward lasing technique ,Physical and Theoretical Chemistry ,010306 general physics ,Image resolution ,Streak camera ,business.industry ,Mechanical Engineering ,Laser ,chemistry ,Temporal resolution ,Femtosecond ,business ,Lasing threshold - Abstract
We report on an experimental demonstration of spatially-resolved detection of atomic hydrogen in flames using a single-ended configuration yielding 656-nm lasing in the backward direction upon 2-photon pumping with 205-nm femtosecond laser pulses. Spatial resolution is achieved by temporally-resolved detection of the backward lasing using a streak camera. The method is demonstrated in CH4/O2 flames; both in a setup consisting of two flames, with variable spacing between the flames, and in a single flame. Results from the two-flame experiment show that the backward lasing technique is able to determine changes in the separation between the flames as this distance was altered. By maximizing the temporal resolution of the streak camera, obtaining a highest spatial resolution of 1.65 mm, it is possible to resolve the hydrogen signal present in the two reaction zones in the single flame, where the separation between the reaction zones is ∼2 mm. The lasing signal is strong enough to allow single-shot measurements. Results obtained by backward lasing are compared with 2-photon planar laser-induced fluorescence (LIF) images recorded with detection perpendicular to the laser beam path and the results from the two methods qualitatively agree. Although further studies are needed in order to extract quantitative hydrogen concentrations, the present results indicate great potential for spatially resolved single-ended measurements, which would constitute a very valuable asset for combustion diagnostics in intractable geometries with limited optical access. It appears feasible to extend the technique to detection of any species for which resonant two-photon-excited lasing effect has been observed, such as O, N, C, CO and NH3.
- Published
- 2019
4. Quantitative Imaging of Ozone Vapor Using Photofragmentation Laser-Induced Fluorescence (LIF)
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Wubin Weng, Dina Hot, Marcus Aldén, Kajsa Larsson, Andreas Ehn, Joakim Bood, and Andreas Lantz
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Ozone ,Atom and Molecular Physics and Optics ,medicine.medical_treatment ,Analytical chemistry ,02 engineering and technology ,01 natural sciences ,Fluence ,law.invention ,010309 optics ,chemistry.chemical_compound ,Optics ,law ,0103 physical sciences ,medicine ,Absorption (electromagnetic radiation) ,Laser-induced fluorescence ,Instrumentation ,Spectroscopy ,Detection limit ,Excimer laser ,LIF ,business.industry ,imaging ,021001 nanoscience & nanotechnology ,Laser ,photofragmentation ,Fluorescence ,laser-induced fluorescence ,chemistry ,13. Climate action ,0210 nano-technology ,business - Abstract
In the present work, the spectral properties of gaseous ozone (O3) have been investigated aiming to perform quantitative concentration imaging of ozone by using a single laser pulse at 248 nm from a KrF excimer laser. The O3 molecule is first photodissociated by the laser pulse into two fragments, O and O2. Then the same laser pulse electronically excites the O2 fragment, which is vibrationally hot, whereupon fluorescence is emitted. The fluorescence intensity is found to be proportional to the concentration of ozone. Both emission and absorption characteristics have been investigated, as well as how the laser fluence affects the fluorescence signal. Quantitative ozone imaging data have been achieved based on calibration measurements in known mixtures of O3. In addition, a simultaneous study of the emission intensity captured by an intensified charge-coupled device (ICCD) camera and a spectrograph has been performed. The results show that any signal contribution not stemming from ozone is negligible compared to the strong fluorescence induced by the O2 fragment, thus proving interference-free ozone imaging. The single-shot detection limit has been estimated to ∼400 ppm. The authors believe that the presented technique offers a valuable tool applicable in various research fields, such as plasma sterilization, water and soil remediation, and plasma-assisted combustion.
- Published
- 2017
5. Detection of atomic oxygen in a plasma-assisted flame via a backward lasing technique
- Author
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Joakim Bood, Deanna A. Lacoste, Andreas Ehn, Pengji Ding, Davide Del Cont-Bernard, and Maria Ruchkina
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Materials science ,business.industry ,Atom and Molecular Physics and Optics ,Physics::Optics ,02 engineering and technology ,Plasma ,Nanosecond ,021001 nanoscience & nanotechnology ,Laser ,01 natural sciences ,Signal ,Atomic and Molecular Physics, and Optics ,law.invention ,010309 optics ,Optics ,law ,0103 physical sciences ,Femtosecond ,Spontaneous emission ,Atomic physics ,Physics::Chemical Physics ,0210 nano-technology ,business ,Laser-induced fluorescence ,Lasing threshold - Abstract
In this Letter, we have investigated 845 nm lasing generation in atomic oxygen, present in a lean methane-air flame, using two-photon pumping with femtosecond 226 nm laser pulses, particularly focusing on the impact of nanosecond repetitively pulsed glow discharges forcing on the backward lasing signal. Characterizations of the backward lasing pulse, in terms of its spectrum, beam profile, pump pulse energy dependence, and divergence, were conducted to establish the presence of lasing. With plasma forcing of the flame, the backward lasing signal was observed to be enhanced significantly, ∼50%. The vertical concentration profile of atomic oxygen was revealed by measuring the backward lasing signal strength as a function of height in the flame. The results are qualitatively consistent with results obtained with two-dimensional femtosecond two-photon-absorption laser-induced fluorescence, suggesting that the backward lasing technique can be a useful tool for studies of plasma-assisted combustion processes, particularly in geometries requiring single-ended standoff detection.
- Published
- 2019
6. Improved spectral sensitivity by combining periodic shadowing and high dynamic range imaging
- Author
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Elias Kristensson and Andreas Ehn
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Physics ,Spectrometer ,Stray light ,Dynamic range ,business.industry ,Detector ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Analytical Chemistry ,010309 optics ,Spectral sensitivity ,Optics ,High-dynamic-range imaging ,0103 physical sciences ,Emission spectrum ,0210 nano-technology ,Spectroscopy ,business - Abstract
Most emission spectra are characterized by lines of various intensities, a feature making them difficult to probe in their entirety - the limited dynamic range of the detector prohibits the simultaneous observation of both weak and intense spectral features. A further known complication in spectroscopy concerns the generation and detection of stray light, which is an undesired contribution of light, often associated with unavoidable imperfections in the spectrometer. Stray light leads to an offset that often exceeds the intensity of weak lines, especially those that were barely detectable in the absence of stray light. This problem is well-known in, for example, laser-induced Raman spectroscopic measurements. In this paper, we describe a methodology to solve both the stray light problem and that associated with the limited dynamic range of the detector. The method is based on combining the high dynamic range imaging concept commonly employed in digital photography with the periodic shadowing technique, where the former is used to boost the dynamics and the latter to suppress stray light. The capabilities of the approach, which is suitable for investigation of temporally stable sources, are demonstrated and the results are compared with measurements performed with both conventional equipment and the periodic shadowing technique. (Less)
- Published
- 2015
7. Advanced Laser-Based Techniques for Gas-Phase Diagnostics in Combustion and Aerospace Engineering
- Author
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Andreas Ehn, Xuesong Li, Johannes Kiefer, and Jiajian Zhu
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Materials science ,Technische Fakultät ,02 engineering and technology ,Combustion ,01 natural sciences ,law.invention ,Physics::Fluid Dynamics ,010309 optics ,symbols.namesake ,law ,0103 physical sciences ,Physics::Atomic Physics ,Rayleigh scattering ,Aerospace engineering ,Instrumentation ,Spectroscopy ,Scattering ,business.industry ,Pulse duration ,Laser Doppler velocimetry ,021001 nanoscience & nanotechnology ,Laser ,Particle image velocimetry ,symbols ,ddc:620 ,0210 nano-technology ,business ,Raman scattering - Abstract
Gaining information of species, temperature, and velocity distributions in turbulent combustion and high-speed reactive flows is challenging, particularly for conducting measurements without influencing the experimental object itself. The use of optical and spectroscopic techniques, and in particular laser-based diagnostics, has shown outstanding abilities for performing non-intrusive in situ diagnostics. The development of instrumentation, such as robust lasers with high pulse energy, ultra-short pulse duration, and high repetition rate along with digitized cameras exhibiting high sensitivity, large dynamic range, and frame rates on the order of MHz, has opened up for temporally and spatially resolved volumetric measurements of extreme dynamics and complexities. The aim of this article is to present selected important laser-based techniques for gas-phase diagnostics focusing on their applications in combustion and aerospace engineering. Applicable laser-based techniques for investigations of turbulent flows and combustion such as planar laser-induced fluorescence, Raman and Rayleigh scattering, coherent anti-Stokes Raman scattering, laser-induced grating scattering, particle image velocimetry, laser Doppler anemometry, and tomographic imaging are reviewed and described with some background physics. In addition, demands on instrumentation are further discussed to give insight in the possibilities that are offered by laser flow diagnostics.
- Published
- 2017
8. High dynamic spectroscopy using a digital micromirror device and periodic shadowing
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Elias Kristensson, Andreas Ehn, and Edouard Berrocal
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Physics ,Stray light ,Dynamic range ,business.industry ,Atom and Molecular Physics and Optics ,010401 analytical chemistry ,01 natural sciences ,Signal ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Digital micromirror device ,law.invention ,010309 optics ,Optics ,law ,0103 physical sciences ,Charge-coupled device ,Image sensor ,business ,Adaptive optics ,High dynamic range - Abstract
We present an optical solution called DMD-PS to boost the dynamic range of 2D imaging spectroscopic measurements up to 22 bits by incorporating a digital micromirror device (DMD) prior to detection in combination with the periodic shadowing (PS) approach. In contrast to high dynamic range (HDR), where the dynamic range is increased by recording several images at different exposure times, the current approach has the potential of improving the dynamic range from a single exposure and without saturation of the CCD sensor. In the procedure, the spectrum is imaged onto the DMD that selectively reduces the reflection from the intense spectral lines, allowing the signal from the weaker lines to be increased by a factor of 28 via longer exposure times, higher camera gains or increased laser power. This manipulation of the spectrum can either be based on a priori knowledge of the spectrum or by first performing a calibration measurement to sense the intensity distribution. The resulting benefits in detection sensitivity come, however, at the cost of strong generation of interfering stray light. To solve this issue the Periodic Shadowing technique, which is based on spatial light modulation, is also employed. In this proof-of-concept article we describe the full methodology of DMD-PS and demonstrate – using the calibration-based concept – an improvement in dynamic range by a factor of ~100 over conventional imaging spectroscopy. The dynamic range of the presented approach will directly benefit from future technological development of DMDs and camera sensors.
- Published
- 2017
9. Investigations of Microwave Stimulation of Turbulent Flames with Implications to Gas Turbine Combustors
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Christer Fureby, P. Petersson, Marcus Aldén, Zhongshan Li, N. Zettervall, Jenny Larfeldt, Elna J.K. Nilsson, Tomas Hurtig, and Andreas Ehn
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Flexibility (engineering) ,Waste management ,Hydrogen ,business.industry ,Chemistry ,Electric potential energy ,Fossil fuel ,chemistry.chemical_element ,02 engineering and technology ,Combustion ,medicine.disease_cause ,01 natural sciences ,7. Clean energy ,Energy engineering ,Soot ,010305 fluids & plasmas ,Electricity generation ,020401 chemical engineering ,13. Climate action ,0103 physical sciences ,medicine ,0204 chemical engineering ,business ,Process engineering - Abstract
Efficient and clean production of electrical energy and mechanical (shaft) energy for use in industrial and domestic applications, surface- and ground transportation and aero-propulsion is currently of significant general concern. Fossil fuels are mainly used for transportation and aero-propulsion, but also for power generation. Combustion of fossil fuels typically give rise to undesired emissions such as unburned hydrocarbons, carbon dioxide, carbon monoxide, soot and nitrogen oxides. The most widespread approach to minimize these is to apply various lean-burn technologies, and sometimes also dilute the fuel with hydrogen. Although efficient in reducing emissions, lean-burn often results in combustion instabilities and igniteon issues, and thus become challenging itself. Another desired aspect of today’s engines is to increase the fuel flexibility. One possible technique that may be useful for circumventing these issues is plasma-assisted combustion, i.e. to supply a small amount of electric energy to the flame to stimulate the chemical kinetics. Although not new, this approach has not yet been fully explored, partly because of it’s complexity, and partly because of apparent sufficiency. Recently, however, several research studies of this area have emerged. This paper attempts to provide a brief summary of microwave-assisted combustion, in which microwaves are utilized to supply the electrical energy to the flame, and to demonstrate that this method is useful to enhance flame stabilization, delay lean blow-off, and to increase combustion efficiency. The main effect of microwaves (or electrical energy) is to enhance the chemical kinetics, resulting in increased reactivity and laminar and turbulent flame speeds. Here we will demonstrate that this will improve the performance of gas turbine combustors. (Less)
- Published
- 2017
10. FRAME: femtosecond videography for atomic and molecular dynamics
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Elias Kristensson, Edouard Berrocal, Marcus Aldén, Andreas Ehn, Joakim Bood, and Zheming Li
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Measurement point ,videography ,business.industry ,ultrafast photonics ,Physics::Optics ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,imaging techniques ,Electronic, Optical and Magnetic Materials ,010309 optics ,ultrafast spectroscopy ,Molecular dynamics ,Wavelength ,Optics ,Temporal resolution ,0103 physical sciences ,Femtosecond ,High temporal resolution ,Original Article ,0210 nano-technology ,Videography ,business ,Ultrashort pulse - Abstract
Many important scientific questions in physics, chemistry and biology require effective methodologies to spectroscopically probe ultrafast intra- and inter-atomic/molecular dynamics. However, current methods that extend into the femtosecond regime are capable of only point measurements or single-snapshot visualizations and thus lack the capability to perform ultrafast spectroscopic videography of dynamic single events. Here we present a laser-probe-based method that enables two-dimensional videography at ultrafast timescales (femtosecond and shorter) of single, non-repetitive events. The method is based on superimposing a structural code onto the illumination to encrypt a single event, which is then deciphered in a post-processing step. This coding strategy enables laser probing with arbitrary wavelengths/bandwidths to collect signals with indiscriminate spectral information, thus allowing for ultrafast videography with full spectroscopic capability. To demonstrate the high temporal resolution of our method, we present videography of light propagation with record high 200 femtosecond temporal resolution. The method is widely applicable for studying a multitude of dynamical processes in physics, chemistry and biology over a wide range of time scales. Because the minimum frame separation (temporal resolution) is dictated by only the laser pulse duration, attosecond-laser technology may further increase video rates by several orders of magnitude.
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- 2017
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11. Simultaneous one-dimensional fluorescence lifetime measurements of OH and CO in premixed flames
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Joakim Bood, Moah Christensen, Malin Jonsson, Marcus Aldén, and Andreas Ehn
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Materials science ,Quenching (fluorescence) ,Physics and Astronomy (miscellaneous) ,business.industry ,Streak camera ,General Engineering ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Laser ,7. Clean energy ,01 natural sciences ,Fluorescence ,Optical parametric amplifier ,Molecular physics ,law.invention ,010309 optics ,Wavelength ,Optics ,law ,0103 physical sciences ,0210 nano-technology ,Adiabatic process ,business ,Laser-induced fluorescence - Abstract
A method for simultaneous measurements of fluorescence lifetimes of two species along a line is described. The experimental setup is based on picosecond laser pulses from two tunable optical parametric generator/optical parametric amplifier systems together with a streak camera. With an appropriate optical time delay between the two laser pulses, whose wavelengths are tuned to excite two different species, laser-induced fluorescence can be both detected temporally and spatially resolved by the streak camera. Hence, our method enables one-dimensional imaging of fluorescence lifetimes of two species in the same streak camera recording. The concept is demonstrated for fluorescence lifetime measurements of CO and OH in a laminar methane/air flame on a Bunsen-type burner. Measurements were taken in flames with four different equivalence ratios, namely ϕ = 0.9, 1.0, 1.15, and 1.25. The measured one-dimensional lifetime profiles generally agree well with lifetimes calculated from quenching cross sections found in the literature and quencher concentrations predicted by the GRI 3.0 mechanism. For OH, there is a systematic deviation of approximately 30 % between calculated and measured lifetimes. It is found that this is mainly due to the adiabatic assumption regarding the flame and uncertainty in H2O quenching cross section. This emphasizes the strength of measuring the quenching rates rather than relying on models. The measurement concept might be useful for single-shot measurements of fluorescence lifetimes of several species pairs of vital importance in combustion processes, hence allowing fluorescence signals to be corrected for quenching and ultimately yield quantitative concentration profiles.
- Published
- 2013
12. Temporal filtering with fast ICCD cameras in Raman studies
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M. Levenius, Andreas Ehn, Joakim Bood, Marcus Aldén, and Malin Jonsson
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Background subtraction ,Chemistry ,business.industry ,010401 analytical chemistry ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Streak ,Laser ,Polarization (waves) ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,law.invention ,010309 optics ,symbols.namesake ,Optics ,law ,0103 physical sciences ,symbols ,General Materials Science ,Raman spectroscopy ,business ,Spectroscopy ,Raman scattering ,Jitter - Abstract
A common problem when applying Raman scattering in applied research is spectral interference from laser-induced fluorescence. Extensive work has been invested in developing spectral and polarization filters as well as modulation schemes to refine spontaneous Raman signals. This current work, however, focuses on utilizing the temporal domain using a picosecond laser system and ICCD cameras with relatively short decay of the camera gate to prevent the fluorescence tail from being captured in Raman experiments. Further, the approach of using an ICCD camera to perform temporal filtering is compared to earlier proposed detection schemes using streak cameras or Kerr gates. The temporal-filtering scheme is evaluated in a spectroscopic investigation where a background subtraction algorithm is presented. The temporal-filtering scheme was also evaluated for Raman imaging of a levitated water droplet surrounded by fluorescing toluene vapor. Furthermore, the temporal-filter detection scheme was simulated in order to provide straight forward evaluation tools to estimate the potential of performing temporal filtering with a laser/camera system considering: laser-pulse duration, time jitter, camera-gate characteristics, gate delay times, fluorescence lifetimes, and relative signal strength between the Raman and fluorescence signal. The fluorescence signal was modeled with a closed two-level system, and the simulated results were compared to results from an investigation of the rising slope of toluene fluorescence. These evaluation tools and experimental investigations may serve as guidelines for planning and performing Raman measurements in situations where traditional filter-rejection schemes are insufficient. Copyright (c) 2013 John Wiley & Sons, Ltd. (Less)
- Published
- 2013
13. Investigation of Ozone Stimulated Combustion in the SGT-800 Burner at Atmospheric Conditions
- Author
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Jiajian Zhu, Elna J.K. Nilsson, Zhongshan Li, Andreas Ehn, Marcus Aldén, Jenny Larfeldt, Arman Ahamed Subash, and Andreas Lantz
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Pressure drop ,Atmospheric pressure ,Chemistry ,business.industry ,Analytical chemistry ,Industrial gas ,Combustion ,7. Clean energy ,law.invention ,13. Climate action ,Natural gas ,law ,Bunsen burner ,Combustor ,Seeding ,business - Abstract
The effect of ozone (O3) in a turbulent, swirl-stabilized natural gas/air flame was experimentally investigated at atmospheric pressure conditions using planar laser-induced fluorescence imaging of formaldehyde (CH2O PLIF) and dynamic pressure monitoring. The experiment was performed using a dry low emission (DLE) gas turbine burner used in both SGT-700 and SGT-800 industrial gas turbines from Siemens. The burner was mounted in an atmospheric combustion test rig at Siemens with optical access in the flame region. CH2O PLIF imaging was carried out for four different seeding gas compositions and seeding injection channel configurations. Two seeding injection-channels were located around the burner tip while the other two were located along the center axis of the burner at different distances upstream the burner outlet. Four different seeding gas compositions were used: nitrogen (N2), oxygen (O2) and two ozone/oxygen (O3/O2) mixtures with different O3 concentration. The results show that the O3 clearly affects the combustion chemistry. The natural gas/air mixture is preheated before combustion which is shown to kick-start the cold combustion chemistry where O3 is highly involved. The CH2O PLIF signal increases with O3 seeded into the flame which indicates that the pre-combustion activity increases and that the cold chemistry starts to develop further upstream. The small increase of the pressure drop over the burner shows that the flame moves upstream when O3 is seeded into the flame, which confirms the increase in pre-combustion activity.
- Published
- 2016
- Full Text
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14. Setup for microwave stimulation of a turbulent low-swirl flame
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Jenny Larfeldt, Per Petersson, Tomas Hurtig, Andreas Ehn, Marcus Aldén, Christer Fureby, Zhongshan Li, Anders Larsson, and Jiajian Zhu
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microwave enhancement ,Acoustics and Ultrasonics ,Laminar flame speed ,Atom and Molecular Physics and Optics ,020209 energy ,Nozzle ,Analytical chemistry ,02 engineering and technology ,01 natural sciences ,7. Clean energy ,Cylinder (engine) ,law.invention ,Physics::Fluid Dynamics ,010309 optics ,Resonator ,Optics ,law ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Physics::Chemical Physics ,Premixed flame ,plasma-assisted combustion ,business.industry ,Chemistry ,energetically enhanced combustion ,Plasma ,turbulent flames ,Condensed Matter Physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Combustor ,laser diagnosticsvplanar laser-induced fluorescence ,business ,Microwave - Abstract
An experimental setup for microwave stimulation of a turbulent flame is presented. A low-swirl flame is being exposed to continuous microwave irradiation inside an aluminum cavity. The cavity is designed with inlets for laser beams and a viewport for optical access. The aluminum cavity is operated as a resonator where the microwave mode pattern is matched to the position of the flame. Two metal meshes are working as endplates in the resonator, one at the bottom and the other at the top. The lower mesh is located right above the burner nozzle so that the low-swirl flame is able to freely propagate inside the cylinder cavity geometry whereas the upper metal mesh can be tuned to achieve good overlap between the microwave mode pattern and the flame volume. The flow is characterized for operating conditions without microwave irradiation using particle imaging velocimetry (PIV). Microwave absorption is simultaneously monitored with experimental investigations of the flame in terms of exhaust gas temperature, flame chemiluminescence (CL) analysis as well as simultaneous planar laser-induced fluorescence (PLIF) measurements of formaldehyde (CH2O) and hydroxyl radicals (OH). Results are presented for experiments conducted in two different regimes of microwave power. In the high-energy regime the microwave field is strong enough to cause a breakdown in the flame. The breakdown spark develops into a swirl-stabilized plasma due to the continuous microwave stimulation. In the low-energy regime, which is below plasma formation, the flame becomes larger and more stable and it moves upstream closer to the burner nozzle when microwaves are absorbed by the flame. As a result of a larger flame the exhaust gas temperature, flame CL and OH PLIF signals are increased as microwave energy is absorbed by the flame.
- Published
- 2016
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15. Fluorescence lifetime imaging in a flame
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Joakim Bood, Bo Li, Marcus Aldén, Olof Johansson, Andreas Ehn, and Andreas Arvidsson
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Fluorescence-lifetime imaging microscopy ,Quenching (fluorescence) ,business.industry ,Chemistry ,Mechanical Engineering ,General Chemical Engineering ,Analytical chemistry ,Combustion ,Fluorescence ,Optics ,Fluorescence cross-correlation spectroscopy ,Physical and Theoretical Chemistry ,Time-resolved spectroscopy ,business ,Laser-induced fluorescence ,Excitation - Abstract
A novel method for two-dimensional fluorescence lifetime imaging is presented. The technique is demonstrated on averaged planar laser-induced fluorescence (PLIF) signals recorded in a flame. Although demonstrated on averaged images, the concept applies equally well to single-shot images. Formaldehyde was probed through pico-second excitation at 355 nm in a rich methane/oxygen flame (Phi = 2.6). Images were recorded with a dual ICCD camera detection setup with different gate characteristics of the two cameras. The recorded images were analyzed using simulated values of LIF signal detection to generate two-dimensional images of effective lifetimes. Measured lifetimes range from roughly 1 to 4.5 ns. The lifetime image data were used for quenching correction of the LIF images, which, after correction, showed better qualitative agreement compared to a formaldehyde concentration profile simulated with the GRI 3.0 mechanism. (C) 2010 The Combustion Institute. Published by Elsevier Inc. All rights reserved. (Less)
- Published
- 2011
16. Single-shot photofragment imaging by structured illumination
- Author
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Andreas Ehn, Joakim Bood, Marcus Aldén, Malin Jonsson, Elias Kristensson, Kajsa Larsson, and Jesper Borggren
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Materials science ,Stray light ,business.industry ,Laminar flow ,Laser ,Signal ,Atomic and Molecular Physics, and Optics ,Intensity (physics) ,law.invention ,Optics ,law ,Spatial frequency ,Laser-induced fluorescence ,business ,Beam (structure) - Abstract
A laser method to suppress background interferences in pump-probe measurements is presented and demonstrated. The method is based on structured illumination, where the intensity profile of the pump beam is spatially modulated to make its induced photofragment signal distinguishable from that created solely by the probe beam. A spatial lock-in algorithm is then applied on the acquired data, extracting only those image components that are characterized by the encoded structure. The concept is demonstrated for imaging of OH photofragments in a laminar methane/air flame, where the signal from the OH photofragments produced by the pump beam is spatially overlapping with that from the naturally present OH radicals. The purpose was to perform for the first time, to the best of our knowledge, single-shot imaging of HO(2) in a flame. These results show an increase in signal-to-interference ratio of about 20 for single-shot data.
- Published
- 2015
17. Range-resolved detection of potassium chloride using picosecond differential absorption light detection and ranging
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Joakim Bood, Andreas Ehn, Magnus Berg, Christian Brackmann, Tomas Leffler, Billy Kaldvee, and Marcus Aldén
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Detection limit ,Materials science ,business.industry ,Mie scattering ,Differential optical absorption spectroscopy ,Laser ,Chloride ,Atomic and Molecular Physics, and Optics ,law.invention ,Dial ,Optics ,law ,Picosecond ,medicine ,Electrical and Electronic Engineering ,business ,Absorption (electromagnetic radiation) ,Engineering (miscellaneous) ,medicine.drug - Abstract
A laser diagnostic concept for measurement of potassium chloride (KCl) and potentially other alkali compounds in large-scale boilers and furnaces of limited optical access is presented. Single-ended, range-resolved, quantitative detection of KCl is achieved by differential absorption light detection and ranging (DIAL) based on picosecond laser pulses. Picosecond DIAL results have been compared experimentally with line-of-sight measurements using a commercial instrument, the in situ alkali chloride monitor (IACM), utilizing differential optical absorption spectroscopy. For centimeter-scale range resolution and a collection distance of 2.5 m, picosecond DIAL allowed for measurement of KCl concentrations around 130 ppm at 1200 K, in good agreement with values obtained by IACM. The DIAL data indicate a KCl detection limit of around 30 ppm for the present experimental conditions. In addition, a double-pulse DIAL setup has been developed and demonstrated for measurements under dynamic conditions with strong Mie scattering. The picosecond DIAL results are discussed and related to possible implementations of the method for measurements in industrial environments.
- Published
- 2015
18. Advancements in Rayleigh scattering thermometry by means of structured illumination
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Joakim Bood, Andreas Ehn, Elias Kristensson, and Marcus Aldén
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Elastic scattering ,Photon ,Planar Imaging ,Chemistry ,business.industry ,Stray light ,Mechanical Engineering ,General Chemical Engineering ,7. Clean energy ,01 natural sciences ,Temperature measurement ,Signal ,010305 fluids & plasmas ,010309 optics ,symbols.namesake ,Optics ,Interference (communication) ,0103 physical sciences ,symbols ,Physical and Theoretical Chemistry ,Rayleigh scattering ,business - Abstract
Laser-induced Rayleigh scattering is commonly employed for two-dimensional temperature measurements and offers benefits such as high accuracy, easily interpreted data and low experimental complexity. Yet the approach suffers from an interference often referred to as stray light, an umbrella term used for all spurious light being detected. As Rayleigh scattering is an elastic scattering phenomenon, distinguishing between stray light and the signal of interest is not straightforward. In high-temperature environments, Rayleigh signals are weak due to low molecular densities, which make stray light interferences particularly cumbersome, impairing both the reliability and accuracy of Rayleigh thermometry, especially when applied in harsh combustion environments. In this paper we present an experimental solution to greatly mitigate this issue. The method, Structured Laser Illumination Planar Imaging (SLIPI), employs an intensity modulated laser light sheet to add a recognizable signature to the signal photons. This unique signature allows utilization of a post-processing algorithm that isolates and extracts the desired Rayleigh signal, thereby minimizing measurement uncertainties caused by stray light. The fidelity of the proposed method is first verified by comparing with conventional Rayleigh thermometry under ideal, i.e., stray light-free, measurement conditions. The technique is then employed under more realistic measurement conditions, where the results conclusively illustrate that the current operating range for Rayleigh thermometry can be increased significantly by means of SLIPI. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved. (Less)
- Published
- 2014
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19. Single-laser shot fluorescence lifetime imaging on the nanosecond timescale using a Dual Image and Modeling Evaluation algorithm
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Andreas Ehn, Olof Johansson, Andreas Arvidsson, Joakim Bood, and Marcus Aldén
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Fluorescence-lifetime imaging microscopy ,Materials science ,business.industry ,Streak camera ,Atom and Molecular Physics and Optics ,Lasers ,Detector ,Monte Carlo method ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Equipment Design ,Nanosecond ,Laser ,Image Enhancement ,Atomic and Molecular Physics, and Optics ,law.invention ,Equipment Failure Analysis ,Optics ,Microscopy, Fluorescence ,law ,Temporal resolution ,Image Interpretation, Computer-Assisted ,Sensitivity (control systems) ,business ,Algorithms - Abstract
A novel technique, designated dual imaging and modeling evaluation (DIME), for evaluating single-laser shot fluorescence lifetimes is presented. The technique is experimentally verified in a generic gas mixing experiment to provide a clear demonstration of the rapidness and sensitivity of the detector scheme. Single-laser shot fluorescence lifetimes of roughly 800 ps with a standard deviation of similar to 120 ps were determined. These results were compared to streak camera measurements. Furthermore, a general fluorescence lifetime determination algorithm is proposed. The evaluation algorithm has an analytic, linear relationship between the fluorescence lifetime and detector signal ratio. In combination with the DIME detector scheme, it is a faster, more accurate and more sensitive approach for rapid fluorescence lifetime imaging than previously proposed techniques. Monte Carlo simulations were conducted to analyze the sensitivity of the detector scheme as well as to compare the proposed evaluation algorithm to previously presented rapid lifetime determination algorithms. (C) 2012 Optical Society of America
- Published
- 2012
20. Fluorescence lifetime imaging through scattering media using Dual Imaging Modeling Evaluation in combination with Structured Laser Illumination Planar Imaging
- Author
-
Elias Kristensson, Joakim Bood, Andreas Ehn, Olof Johansson, and Marcus Aldén
- Subjects
Fluorescence-lifetime imaging microscopy ,Planar Imaging ,Materials science ,business.industry ,Scattering ,Laminar flow ,Fluorescence ,Dual imaging ,Physics::Fluid Dynamics ,symbols.namesake ,Optics ,Computer Science::Computer Vision and Pattern Recognition ,symbols ,Optoelectronics ,Laser illumination ,Physics::Chemical Physics ,Rayleigh scattering ,business - Abstract
Fluoresce lifetime imaging in combination with structured laser illumination planar imaging has been performed in wide field imaging. Measurements were conducted by imaging laminar gaseous flows seeded with toluene through scattering media.
- Published
- 2012
21. Development of a temporal filtering technique for suppression of interferences in applied laser-induced fluorescence diagnostics
- Author
-
Andreas Ehn, Marcus Aldén, Joakim Bood, and Billy Kaldvee
- Subjects
Materials science ,Streak camera ,business.industry ,Stray light ,Materials Science (miscellaneous) ,Mie scattering ,Filter (signal processing) ,Signal ,Industrial and Manufacturing Engineering ,symbols.namesake ,Optics ,symbols ,Business and International Management ,Rayleigh scattering ,Luminescence ,business ,Laser-induced fluorescence - Abstract
A temporal filtering technique, complementary to spectral filtering, has been developed for laser-induced fluorescence measurements. The filter is applicable in cases where the laser-induced interfering signals and the signal of interest have different temporal characteristics. For the interfering-signal discrimination a picosecond laser system along with a fast time-gated intensified CCD camera were used. In order to demonstrate and evaluate the temporal filtering concept two measurement situations were investigated; one where toluene fluorescence was discriminated from interfering luminescence of an aluminum surface, and in the other one Mie scattering signals from a water aerosol were filtered out from acetone fluorescence images. A mathematical model was developed to simulate and evaluate the temporal filter for a general measurement situation based on pulsed-laser excitation together with time-gated detection. Using system parameters measured with a streak camera, the model was validated for LIF imaging of acetone vapor inside a water aerosol. The results show that the temporal filter is capable of efficient suppression of interfering signal contributions. The photophysical properties of several species commonly studied by LIF in combustion research have been listed and discussed to provide guidelines for optimum use of the technique.
- Published
- 2009
22. Stray light suppression in spectroscopy using periodic shadowing
- Author
-
Joakim Bood, Emil Nordström, Sven Huldt, Edouard Berrocal, Marcus Aldén, Elias Kristensson, Andreas Ehn, Per-Erik Bengtsson, Hampus Nilsson, and Jiajian Zhu
- Subjects
Physics ,Accuracy and precision ,business.industry ,Stray light ,Atom and Molecular Physics and Optics ,Band-stop filter ,Interference (wave propagation) ,Atomic and Molecular Physics, and Optics ,Spectral line ,Optics ,13. Climate action ,Spectroscopy ,Absorption (electromagnetic radiation) ,business ,Visible spectrum - Abstract
It is well known that spectroscopic measurements suffer from an interference known as stray light, causing spectral distortion that reduces measurement accuracy. In severe situations, stray light may even obscure the existence of spectral lines. Here a novel general method is presented, named Periodic Shadowing, that enables effective stray light elimination in spectroscopy and experimental results are provided to demonstrate its capabilities and versatility. Besides its efficiency, implementing it in a spectroscopic arrangement comes at virtually no added experimental complexity. (C) 2014 Optical Society of America
- Published
- 2014
23. Development of a picosecond lidar system for large-scale combustion diagnostics
- Author
-
Billy Kaldvee, Joakim Bood, Marcus Aldén, and Andreas Ehn
- Subjects
Materials science ,Scale (ratio) ,business.industry ,Materials Science (miscellaneous) ,Combustion ,medicine.disease_cause ,Industrial and Manufacturing Engineering ,Soot ,law.invention ,symbols.namesake ,Optics ,Lidar ,law ,Bunsen burner ,Picosecond ,Combustor ,symbols ,medicine ,Business and International Management ,Rayleigh scattering ,business ,Remote sensing - Abstract
In the present work, a picosecond lidar system aiming at single-ended combustion diagnostics in full-scale combustion devices with limited optical access, such as power plants, is described. The highest overall range resolution of the system was found to be
- Published
- 2008
24. Time-resolved polarization lock-in filtering for background suppression in Raman spectroscopy of biomass pyrolysis
- Author
-
Haisol Kim, Andreas Ehn, Miaoxin Gong, Elias Kristensson, Christian Brackmann, and Marcus Aldén
- Subjects
Limiting factor ,Materials science ,General Chemical Engineering ,Atom and Molecular Physics and Optics ,General Physics and Astronomy ,Energy Engineering and Power Technology ,Energy Engineering ,02 engineering and technology ,Biomass pyrolysis ,01 natural sciences ,law.invention ,symbols.namesake ,Laser diagnostics ,020401 chemical engineering ,law ,0103 physical sciences ,0204 chemical engineering ,010304 chemical physics ,business.industry ,General Chemistry ,Filter (signal processing) ,Polarization (waves) ,Laser ,Fluorescence ,Fuel Technology ,Raman spectroscopy ,symbols ,Optoelectronics ,Polarization lock-in filtering ,business ,Pyrolysis ,Excitation - Abstract
Laser-based Raman spectroscopy is a powerful technique for non-intrusive measurements of chemical composition in gas, liquid, and solids. However, weak signals make it challenging to employ the technique for diagnostics under harsh conditions with various background interferences. To overcome such limitations, we have devised a method, polarization lock-in filtering (PLF) based on temporal modulation of the excitation laser polarization, to filter out polarization-independent signals from acquired data. The PLF method applied for continuous Raman spectroscopy measurements of a biomass pyrolysis process showed promising filtering abilities for unwanted background fluorescence signals. A broadband fluorescence background interference was suppressed by up to a factor of 50. Therefore, released species during the biomass pyrolysis process were readily identified with their Raman spectrum signatures and their amounts quantified. In addition, the PLF method provided Raman spectra of low background, from which a gradual change in hydrocarbons released at different stages during the pyrolysis could be observed. Altogether, the efficient background suppression method increases the general applicability of Raman spectroscopy under conditions where interfering signals present a challenge and a limiting factor.
- Full Text
- View/download PDF
25. The Spotify Play: How CEO and Founder Daniel Ek Beat Apple, Google and Amazon in the Race for Audio Dominance
- Subjects
The Spotify Play: How CEO and Founder Daniel Ek Beat Apple, Google and Amazon in the Race for Audio Dominance (Biography) -- Carlsson, Sven -- Leijonhufvud, Jonas ,Books -- Book reviews ,Advertising, marketing and public relations ,Business ,Publishing industry - Abstract
Sven Carlsson and Jonas Leijonhufvud. Diversion, $17.99 trade paper (304p) ISBN 978-1-63576-744-5 Journalists Carlsson and Leijonhufvud trace the victories and struggles of a startup turned behemoth in this fawning corporate [...]
- Published
- 2020
26. -Sweden-based Tripbirds relaunches site based on Instagram, Facebook
- Subjects
Computers -- Services ,Social networks -- Usage ,Business ,Transportation industry - Abstract
AIRLINE INDUSTRY INFORMATION-(C)1997-2012 M2 COMMUNICATIONS Stockholm-based startup travel site Tripbirds.com said it has relaunched as a social hotel-booking site. According to the company, the website combines a 'traditional' list of [...]
- Published
- 2012
27. One of the Biggest Startup Events in CEE Countries - Bitspiration Festival - Starts on June 22-23rd at The Palace of Culture and Science in Warsaw
- Subjects
Festivals ,Business ,News, opinion and commentary ,Spotify (Online service) - Abstract
[[para]]WARSAW, Poland, June 16, 2015 /PRNewswire/ --[[/para]] World class speakers, creative entrepreneurs, startupers, tech top journalists, musicians, investors and Internet freaks - they will all gather on June 22-23rd in [...]
- Published
- 2015
28. Bitspiration Festival Set for The Palace of Culture and Science in Warsaw
- Subjects
Festivals ,Business ,Business, international ,Telecommunications industry - Abstract
Bitspiration, a celebration of tech and music in Central and Eastern Europe Central and Eastern Europe, will be held June 22-23rd at The Palace of Culture and Science in Warsaw. [...]
- Published
- 2015
29. Tripbirds Relaunches as Social Hotel Booking Site
- Subjects
Hotels and motels -- Sweden ,Business ,Business, international ,Facebook (Online social network) - Abstract
* Tripbirds, the hottest start-up in Stockholm according to WIRED magazine, relaunches as the first hotel booking site based on Instagram and Facebook * Tripbirds helps you book hotels with [...]
- Published
- 2012
30. Thirteen New Retailers Gift-Wrapped for U.K. Users
- Subjects
Retail industry ,Brand name products ,Company business management ,Business ,Business, international ,News, opinion and commentary ,Facebook (Online social network) - Abstract
Byline: LONDON, Jun 22, 2012 (MARKETWIRE via COMTEX) -- -- Free gift cards from O'Neill, House of Fraser, Lipsy, Firebox, Schuh, Glamour, Eventim, Slurp, and more now available from Wrapp [...]
- Published
- 2012
31. Wrapp Mobile Social Gifting Service Coming to Poland
- Subjects
Telecommunications services industry ,Communications industry ,Telecommunications services industry ,Company business management ,Business ,Business, international ,News, opinion and commentary ,Facebook (Online social network) - Abstract
Byline: WARSAW, POLAND, May 23, 2012 (MARKETWIRE via COMTEX) -- Wrapp, the new social gifting app that lets you give your Facebook friends free gift cards to top national, multinational, [...]
- Published
- 2012
32. Wrapp Set to Bring New Social Gifting Service to Italy
- Subjects
Company business management ,Business ,Business, international ,News, opinion and commentary ,Facebook (Online social network) - Abstract
Byline: MILAN, ITALY, May 16, 2012 (MARKETWIRE via COMTEX) -- eCommerce NETCOMM FORUM 2012 -- Wrapp, the first social gifting service that lets you give your Facebook friends free gift [...]
- Published
- 2012
33. Wrapp Prepares to Introduce Mobile Social Gifting in Brazil
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Creator of Social Gifting Service for Giving Facebook Friends Free Gift Cards From Top Retailers Starts Pre-Launch Phase of Integration With Popular Merchants SAO PAULO -- Wrapp, the new social [...]
- Published
- 2012
34. Wrapp Brings Social Gifting to U.S. with Major Merchants
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Gap, H&M, Sephora, Fab, Angry Birds, Wall Street Journal, Lead First Partners Letting Consumers Give Free Gifts and Promotional Gift Cards to Facebook Friends NEW YORK -- Europe's social gifting [...]
- Published
- 2012
35. Wrapp Social Gifting Service Coming to Turkey
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Original Mobile App for Giving Free Gift Cards to Facebook Friends Allows Retailers to Monetize Social Media Investments and Transform Fans Into a Super Sales Force ISTANBUL -- Wrapp, the [...]
- Published
- 2012
36. Wrapp Social Gifting App Coming to Australia
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Fun Way to Celebrate Friends' Important Moments With Free Gift Cards From Top Retailers; Gives Merchants Premium Display on Facebook, Generates In-Store Sales SYDNEY -- Wrapp, the hot new social [...]
- Published
- 2012
37. Wrapp Prepares for Introduction of Social Gifting in Japan
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Creator of First App for Giving Facebook Friends Free Gift Cards to Top Retailers Opens Offices in Tokyo, Appoints Country Manager, Starts Engaging Merchants TOKYO -- Wrapp is coming to [...]
- Published
- 2012
38. Wrapp Sets up Operations in Netherlands
- Subjects
Brand name products ,Business ,Business, international ,Facebook (Online social network) - Abstract
First Social Gifting App for Giving Facebook Friends Free Gift Cards Receives Warm Reception Among Region's Top Retailers as Global Expansion Continues in Europe AMSTERDAM -- Wrapp, the company that [...]
- Published
- 2012
39. Wrapp Starts Asian Social Gifting Expansion in Taiwan
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Fun Way To Send Facebook Friends Free Gift Cards to Top Retailers; Cards Stored In Your Phone So Always With You When Shopping For Something Really Wanted TAIPEI, Taiwan -- [...]
- Published
- 2012
40. Wrapp Social Gifting Coming to France
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Creator of First Mobile App for Friends to Give Free Gift Cards From Top Retailers to Facebook Friends Opens Operations in Paris; Starts Integration with Merchants PARIS -- Wrapp, the [...]
- Published
- 2012
41. Wrapp Readies German Launch of Original Social Gifting Service
- Subjects
Brand name products ,Company marketing practices ,Business ,Business, international ,Facebook (Online social network) -- Marketing - Abstract
Creator of First Mobile App for Friends to Give Free and Paid Gift Cards From Attractive Brands to Their Facebook Friends Opens German Operations MUNICH -- Wrapp, the leading social [...]
- Published
- 2012
42. Wrapp Activates Social Gifting Service in Norway
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
13 Top Merchants including Indiska, Clas Ohlson, Granit, Amazon's Lovefilm, Bjorn Borg, WeSC, Triwa, EuroFlorist, Happy Socks, Ellos, Kick Off Nordic Expansion STOCKHOLM -- Wrapp, the social gifting app that [...]
- Published
- 2012
43. Tripbirds Flies out of Private Beta
- Subjects
Index Ventures ,Travel -- Sweden -- United States ,Business ,Business, international ,Facebook (Online social network) - Abstract
* Tripbirds uses your friends' Facebook and Foursquare check-ins and geo-tagged Instagram pictures to recommend places to visit, stay, eat and explore * The Stockholm based start-up is backed by [...]
- Published
- 2012
44. Wrapp Starts Global Expansion of Social Gifting Service in U.K
- Subjects
Business ,Business, international ,Facebook (Online social network) - Abstract
Aurora Fashions, ASOS, Theater Tokens, Fitness First, Lead Charter Merchant Partners Making Wrapp's Friend-to-Friend Gift Giving an Everyday Event LONDON -- Wrapp, the leading social gifting app for celebrating, thanking, [...]
- Published
- 2012
45. LinkedIn Co-Founder Reid Hoffman Joins Skype Co-Founder Niklas Zennstrom on Wrapp Board as Greylock Adds $5 Million to Series A
- Subjects
Greylock Partners ,Venture capital companies ,Business ,Business, international - Abstract
STOCKHOLM -- Wrapp, the new social gifting service, today announced that Greylock Partners is adding $5 million to the company's Series A funding and co-leading the round with Atomico, the [...]
- Published
- 2012
46. Skype Co-Founder Niklas Zennstrom Joins Board of Wrapp Social Gifting Service as Atomico Leads $5.5 Million Series A Funding
- Subjects
Venture capital companies ,Business ,Business, international - Abstract
STOCKHOLM -- Wrapp, the new social gifting service that lets friends celebrate with free gifts of real value from attractive brands, today announced it has received $5.5 million in Series [...]
- Published
- 2011
47. Wrapp Readies U.S. and U.K. Launch of Social Gifting Service
- Subjects
Company marketing practices ,Company service introduction ,Business ,Business, international - Abstract
Mobile App for Friends to Give Free and Paid Digital Gift Cards From Attractive Brands Receives Rave Reviews in Swedish Tests; U.K. Retailers Begin Signing Up SAN FRANCISCO -- Wrapp, [...]
- Published
- 2011
48. -Sweden-based Tripbirds relaunches site based on Instagram, Facebook
- Subjects
Business ,Facebook (Online social network) - Abstract
M2 EQUITYBITES-September 4, 2012--Sweden-based Tripbirds relaunches site based on Instagram, Facebook(C)2012 M2 COMMUNICATIONS http://www.m2.com Stockholm-based startup travel site Tripbirds.com said it has relaunched as a social hotel-booking site. According to [...]
- Published
- 2012
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