| 1. |
- Ceco, Ema, et al.
(författare)
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The detection limit of imaging Raman spectroscopy for 2,4,6-TNT, 2,4-DNT, and RDX
- 2012
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Ingår i: Optics and photonics for counterterrorism, crime fighting, and defence VIII. - : SPIE - International Society for Optical Engineering. ; , s. 854604-
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Konferensbidrag (refereegranskat)abstract
- At the Swedish Defence Research Agency, FOI, Raman spectroscopy is used to detect explosives at stand-off distances. A technique based on imaging Raman spectroscopy has been shown to have the potential to detect trace amounts of explosives at stand-off distances. In this publication we provide limits of detection with the current imaging Raman setup for four different substances, cyclotrimethylenetrinitramine (RDX), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), and sulfur. The limits of detection for DNT and TNT were found to be about 0,5 μg while the lowest limit of detection was achieved for sulfur at 200 ng. The detection limit for RDX is 25,9 μg.
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| 2. |
- Conley, Daniel, et al.
(författare)
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Hypoxia-Related Processes in the Baltic Sea
- 2009
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 43:10, s. 3412-3420
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia, a growing worldwide problem, has been intermittently present in the modern Baltic Sea since its formation ca. 8000 cal. yr BP. However, both the spatial extent and intensity of hypoxia have increased with anthropogenic eutrophication due to nutrient inputs. Physical processes, which control stratification and the renewal of oxygen in bottom waters, are important constraints on the formation and maintenance of hypoxia. Climate controlled inflows of saline water from the North Sea through the Danish Straits is a critical controlling factor governing the spatial extent and duration of hypoxia. Hypoxia regulates the biogeochemical cycles of both phosphorus (P) and nitrogen (N) in the water column and sediments. Significant amounts of P are currently released from sediments, an order of magnitude larger than anthropogenic inputs. The Baltic Sea is unique for coastal marine ecosystems experiencing N losses in hypoxic waters below the halocline. Although benthic communities in the Baltic Sea are naturally constrained by salinity gradients, hypoxia has resulted in habitat loss over vast areas and the elimination of benthic fauna, and has severely disrupted benthic food webs. Nutrient load reductions are needed to reduce the extent, severity, and effects of hypoxia.
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| 3. |
- Eek, Jacob, et al.
(författare)
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A Novel and Fast Approach for Reconstructing CASSI-Raman Spectra using Generative Adversarial Networks
- 2022
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Ingår i: 2022 ELEVENTH INTERNATIONAL CONFERENCE ON IMAGE PROCESSING THEORY, TOOLS AND APPLICATIONS (IPTA). - : IEEE. - 9781665469647 - 9781665469654
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Konferensbidrag (refereegranskat)abstract
- Raman spectroscopy in conjunction with a Coded Aperture Snapshot Spectral Imaging (CASSI) system allows for detection of small amounts of explosives from stand-off distances. The obtained Compressed Sensing (CS) measurements from CASSI consists of mixed spatial and spectral information, from which a HyperSpectral Image (HSI) can be reconstructed. The HSI contains Raman spectra for all spatial locations in the scene, revealing the existence of substances. In this paper we present the possibility of utilizing a learned prior in the form of a conditional generative model for HSI reconstruction using CS. A Generative Adversarial Network (GAN) is trained using simulated samples of HSI, and conditioning on their respective CASSI measurements to refine the prior. Two different types of simulated HSI were investigated, where spatial overlap of substances was either allowed or disallowed. The results show that the developed method produces precise reconstructions of HSI from their CASSI measurements in a matter of seconds.
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| 4. |
- Glimtoft, Martin, et al.
(författare)
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Digital micromirror devices in Raman trace detection of explosives
- 2016
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Ingår i: Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XXI. - : SPIE - International Society for Optical Engineering. - 9781510600645
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Konferensbidrag (refereegranskat)abstract
- Imaging Raman spectroscopy based on tunable filters is an established technique for detecting single explosives particles at stand-off distances. However, large light losses are inherent in the design due to sequential imaging at different wavelengths, leading to effective transmission often well below 1 %. The use of digital micromirror devices (DMD) and compressive sensing (CS) in imaging Raman explosives trace detection can improve light throughput and add significant flexibility compared to existing systems. DMDs are based on mature microelectronics technology, and are compact, scalable, and can be customized for specific tasks, including new functions not available with current technologies. This paper has been focusing on investigating how a DMD can be used when applying CS-based imaging Raman spectroscopy on stand-off explosives trace detection, and evaluating the performance in terms of light throughput, image reconstruction ability and potential detection limits. This type of setup also gives the possibility to combine imaging Raman with non-spatially resolved fluorescence suppression techniques, such as Kerr gating. The system used consists of a 2nd harmonics Nd:YAG laser for sample excitation, collection optics, DMD, CMOS-camera and a spectrometer with ICCD camera for signal gating and detection. Initial results for compressive sensing imaging Raman shows a stable reconstruction procedure even at low signals and in presence of interfering background signal. It is also shown to give increased effective light transmission without sacrificing molecular specificity or area coverage compared to filter based imaging Raman. At the same time it adds flexibility so the setup can be customized for new functionality.
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| 5. |
- Hanson, Charles, 1958, et al.
(författare)
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Transplantation of human embryonic stem cells onto a partially wounded human cornea in vitro.
- 2013
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Ingår i: Acta ophthalmologica. - : Wiley. - 1755-3768 .- 1755-375X. ; 91:2, s. 127-130
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of this study was to investigate whether cells originating from human embryonic stem cells (hESCs) could be successfully transplanted onto a partially wounded human cornea. A second aim was to study the ability of the transplanted cells to differentiate into corneal epithelial-like cells. Methods: Spontaneously, differentiated hESCs were transplanted onto a human corneal button (without limbus) with the epithelial layer partially removed. The cells were cultured on Bowman's membrane for up to 9days, and the culture dynamics documented in a time-lapse system. As the transplanted cells originated from a genetically engineered hESC line, they all expressed green fluorescent protein, which facilitated their identification during the culture experiments, tissue preparation and analysis. To detect any differentiation into human corneal epithelial-like cells, we analysed the transplanted cells by immunohistochemistry using antibodies specific for CK3, CK15 and PAX6. Results: The transplanted cells established and expanded on Bowman's membrane, forming a 1-4 cell layer surrounded by host corneal epithelial cells. Expression of the corneal marker PAX6 appeared 3days after transplantation, and after 6days, the cells were expressing both PAX6 and CK3. Conclusion: This shows that it is possible to transplant cells originating from hESCs onto Bowman's membrane with the epithelial layer partially removed and to get these cells to establish, grow and differentiate into corneal epithelial-like cells in vitro.
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| 6. |
- Herukka, Sanna-Kaisa, et al.
(författare)
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Recommendations for cerebrospinal fluid Alzheimer's disease biomarkers in the diagnostic evaluation of mild cognitive impairment.
- 2017
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Ingår i: Alzheimer's & dementia : the journal of the Alzheimer's Association. - : Wiley. - 1552-5279. ; 13:3, s. 285-295
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Tidskriftsartikel (refereegranskat)abstract
- This article presents recommendations, based on the Grading of Recommendations, Assessment, Development, and Evaluation method, for the clinical application of cerebrospinal fluid (CSF) amyloid-β1-42, tau, and phosphorylated tau in the diagnostic evaluation of patients with mild cognitive impairment (MCI). The recommendations were developed by a multidisciplinary working group and based on the available evidence and consensus from focused group discussions for 1) prediction of clinical progression to Alzheimer's disease (AD) dementia, 2) cost-effectiveness, 3) interpretation of results, and 4) patient counseling. The working group recommended using CSF AD biomarkers in the diagnostic workup of MCI patients, after prebiomarker counseling, as an add-on to clinical evaluation to predict functional decline or conversion to AD dementia and to guide disease management. Because of insufficient evidence, it was uncertain whether CSF AD biomarkers outperform imaging biomarkers. Furthermore, the working group provided recommendations for interpretation of ambiguous CSF biomarker results and for pre- and post-biomarker counseling.
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| 7. |
- Leuzy, Antoine, et al.
(författare)
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Pittsburgh compound B imaging and cerebrospinal fluid amyloid-β in a multicentre European memory clinic study.
- 2016
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Ingår i: Brain : a journal of neurology. - : Oxford University Press (OUP). - 1460-2156. ; 139:Pt 9, s. 2540-53
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to assess the agreement between data on cerebral amyloidosis, derived using Pittsburgh compound B positron emission tomography and (i) multi-laboratory INNOTEST enzyme linked immunosorbent assay derived cerebrospinal fluid concentrations of amyloid-β42; (ii) centrally measured cerebrospinal fluid amyloid-β42 using a Meso Scale Discovery enzyme linked immunosorbent assay; and (iii) cerebrospinal fluid amyloid-β42 centrally measured using an antibody-independent mass spectrometry-based reference method. Moreover, we examined the hypothesis that discordance between amyloid biomarker measurements may be due to interindividual differences in total amyloid-β production, by using the ratio of amyloid-β42 to amyloid-β40 Our study population consisted of 243 subjects from seven centres belonging to the Biomarkers for Alzheimer's and Parkinson's Disease Initiative, and included subjects with normal cognition and patients with mild cognitive impairment, Alzheimer's disease dementia, frontotemporal dementia, and vascular dementia. All had Pittsburgh compound B positron emission tomography data, cerebrospinal fluid INNOTEST amyloid-β42 values, and cerebrospinal fluid samples available for reanalysis. Cerebrospinal fluid samples were reanalysed (amyloid-β42 and amyloid-β40) using Meso Scale Discovery electrochemiluminescence enzyme linked immunosorbent assay technology, and a novel, antibody-independent, mass spectrometry reference method. Pittsburgh compound B standardized uptake value ratio results were scaled using the Centiloid method. Concordance between Meso Scale Discovery/mass spectrometry reference measurement procedure findings and Pittsburgh compound B was high in subjects with mild cognitive impairment and Alzheimer's disease, while more variable results were observed for cognitively normal and non-Alzheimer's disease groups. Agreement between Pittsburgh compound B classification and Meso Scale Discovery/mass spectrometry reference measurement procedure findings was further improved when using amyloid-β42/40 Agreement between Pittsburgh compound B visual ratings and Centiloids was near complete. Despite improved agreement between Pittsburgh compound B and centrally analysed cerebrospinal fluid, a minority of subjects showed discordant findings. While future studies are needed, our results suggest that amyloid biomarker results may not be interchangeable in some individuals.
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| 8. |
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| 9. |
- Nordberg, Markus, et al.
(författare)
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Detection limit of imaging Raman spectroscopy
- 2012
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Ingår i: Detection and Sensing of Mines, Explosive Objects, and Obscured Targets XVII. - : SPIE - International Society for Optical Engineering.
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Konferensbidrag (refereegranskat)abstract
- Multispectral imaging Raman spectroscopy is a novel technique for detecting and identifying explosive residues, e.g. explosives particles which are left on surfaces after handling or manufacturing of explosives. By imaging a suspect surface using the imaging Raman technique, explosives particles at stand-off distances can be identified and displayed using color coding1. In this paper we present an attempt to determine a limit of detection for imaging Raman spectroscopy by analyzing holes of various sizes in aluminum plates filled with four different substances; 2,4-dinitrotoulene (DNT), ammonium nitrate (AN), sulfur, and 2,4,6-trinitrotoulene (TNT). The detection time in the presented experiments has not been optimized, instead more effort has been invested in order to reduce false alarms. The detection system used is equipped with a green second harmonic Nd:YAG laser with an average power of 2 W, a 200 mm telescope and a liquid crystal tunable filter to scan the wavenumbers. The distance to the target was 10 m and the imaged area was 28 mm × 28 mm. The measured multi-spectral data cubes were evaluated using least square fitting to distinguish between DNT, AN,S, TNT and the background. The detection limit has been determined to be sub microgram using the current setup.
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| 10. |
- Nordberg, Markus, et al.
(författare)
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Stand-off detection of explosive particles by imaging Raman spectroscopy
- 2011
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Ingår i: Proc SPIE Int Soc Opt Eng. - : SPIE. - 9780819485915
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Konferensbidrag (refereegranskat)abstract
- A multispectral imaging technique has been developed to detect and identify explosive particles, e.g. from a fingerprint, at stand-off distances using Raman spectroscopy. When handling IED's as well as other explosive devices, residues can easily be transferred via fingerprints onto other surfaces e.g. car handles, gear sticks and suite cases. By imaging the surface using multispectral imaging Raman technique the explosive particles can be identified and displayed using color-coding. The technique has been demonstrated by detecting fingerprints containing significant amounts of 2,4-dinitrotoulene (DNT), 2,4,6-trinitrotoulene (TNT) and ammonium nitrate at a distance of 12 m in less than 90 seconds (22 images × 4 seconds)1. For each measurement, a sequence of images, one image for each wave number, is recorded. The spectral data from each pixel is compared with reference spectra of the substances to be detected. The pixels are marked with different colors corresponding to the detected substances in the fingerprint. The system has now been further developed to become less complex and thereby less sensitive to the environment such as temperature fluctuations. The optical resolution has been improved to less than 70 μm measured at 546 nm wavelength. The total detection time is ranging from less then one minute to around five minutes depending on the size of the particles and how confident the identification should be. The results indicate a great potential for multi-spectral imaging Raman spectroscopy as a stand-off technique for detection of single explosive particles.
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