In situ monitoring of powder blending by non-invasive Raman spectrometry with wide area illumination

A 785 nm diode laser and probe with a 6 mm spot size were used to obtain spectra of stationary powders and powders mixing at 50 rpm in a high shear convective blender. Two methods of assessing the effect of particle characteristics on the Raman sampling depth for microcrystalline cellulose (Avicel), aspirin or sodium nitrate were compared: (i) the information depth, based on the diminishing Raman signal of TiO2 in a reference plate as the depth of powder prior to the plate was increased, and (ii) the depth at which a sample became infinitely thick, based on the depth of powder at which the Raman signal of the compound became constant The particle size, shape, density and/or light absorption capability of the compounds were shown to affect the "information" and "infinitely thick" depths of individual compounds. However, when different sized fractions of aspirin were added to Avicel as the main component, the depth values of aspirin were the same and matched that of the Avicel: 1.7 mm for the "information" depth and 3.5 mm for the "infinitely thick" depth. This latter value was considered to be the minimum Raman sampling depth when monitoring the addition of aspirin to Avicel in the blender. Mixing profiles for aspirin were obtained non-invasively through the glass wall of the vessel and could be used to assess how the aspirin blended into the main component, identify the end point of the mixing process (which varied with the particle size of the aspirin), and determine the concentration of aspirin in real time. The Raman procedure was compared to two other non-invasive monitoring techniques, near infrared (NIR) spectrometry and broadband acoustic emission spectrometry. The features of the mixing profiles generated by the three techniques were similar for addition of aspirin to Avicel. Although Raman was less sensitive than NIR spectrometry, Raman allowed compound specific mixing profiles to be generated by studying the mixing behaviour of an aspirin-aspartame-Avicel mixture

Comparison of the determination of a low-concentration active ingredient in pharmaceutical tablets by backscatter and transmission raman spectrometry

A total of 383 tablets of a pharmaceutical product were analyzed by backscatter and transmission Raman spectrometry to determine the concentration of an active pharmaceutical ingredient (API), chlorpheniramine maleate, at the 2% m/m (4 mg) level. As the exact composition of the tablets was unknown, external calibration samples were prepared from chlorpheniramine maleate and microcrystalline cellulose (Avicel) of different particle size. The API peak at 1594 cm(-1) in the second derivative Raman spectra was used to generate linear calibration models. The API concentration predicted using backscatter Raman measurements was relatively insensitive to the particle size of Avicel. With transmission, however, particle size effects were greater and accurate prediction of the API content was only possible when the photon propagation properties of the calibration and sample tablets were matched. Good agreement was obtained with HPLC analysis when matched calibration tablets were used for both modes. When the calibration and sample tablets are not chemically matched, spectral normalization based on calculation of relative intensities cannot be used to reduce the effects of differences in physical properties. The main conclusion is that although better for whole tablet analysis, transmission Raman is more sensitive to differences in the photon propagation properties of the calibration and sample tablets

Light trapping in translucent samples and its effect on the hemispherical transmittance obtained by an integrating sphere

When a beam of light is incident on a translucent sample, a significant fraction of the light is scattered at high angles. Some of this scattered light may be trapped inside the substrate through multiple reflections and total internal reflection, similar to light coupling into an optical fiber. The trapping depends on factors such as the surface roughness of the external surfaces and/or the size and distribution of scattering particles inside the sample. The scattered light may thus escape out of the sample at a shifted position relative to the incident beam. This leads to port losses in an integrating sphere. The detected signal from the light entering the sphere then underestimates the hemispherical transmittance. In this paper the signal versus lateral position has been measured in an attempt to estimate the error and to find an extrapolation procedure for the correct transmittance value. The lateral measurements were carried out by moving a detector behind the sample, a procedure carried out at several angles of incidence. Different illumination methods have also been studied both theoretically and experimentally to further investigate what effect light trapping can have when characterising scattering samples

Advanced Synthetic Aperture Radar Based on Digital Beamforming and Waveform Diversity

This paper introduces innovative SAR system concepts for the acquisition of high resolution radar images with wide swath coverage from spaceborne platforms. The new concepts rely on the combination of advanced multi-channel SAR front-end architectures with novel operational modes. The architectures differ regarding their implementation complexity and it is shown that even a low number of channels is already well suited to significantly improve the imaging performance and to overcome fundamental limitations inherent to classical SAR systems. The more advanced concepts employ a multidimensional encoding of the transmitted waveforms to further improve the performance and to enable a new class of hybrid SAR imaging modes that are well suited to satisfy hitherto incompatible user requirements for frequent monitoring and detailed mapping. Implementation specific issues will be discussed and examples demonstrate the potential of the new techniques for different remote sensing applications

Inorganic Nanocrystals And Their Applications In Hybrid 0D:2D Material Optoelectronics

Functional nanomaterials have garnered great interest as candidates for use in next-generational optoelectronics such as solar photovoltaics, light-emitting diodes, and photodetectors. Among these low-dimensional materials, hybrid devices employing both 0D and 2D materials are of interest due to exploitation of the favorable characteristics of each component, and performances superior to standalone counterparts are achievable. This thesis is divided into two parts, as follows. The first two chapters will introduce lowdimensional materials and their favorable characteristics; our work on the formation of ligand-exchanged nanocrystal thin films purified by gel-permeation chromatography will also be discussed. In the second component, the formation and study of two hybrid nanocrystal/epitaxial graphene optoelectronic devices will be presented. My work on a standalone epitaxial graphene/silicon carbide ultraviolet photodetector will also be described

Raman spektroskopi for målinger av matkvalitet i prosesslinjen

A major challenge in the food industry is to effectively handle massive streams of food raw materials and products of different origin and quality. In-line sensor systems for food analysis can potentially measure and collect critical quality and safety parameters throughout the processes. This information can be used for sorting, product differentiation, process optimisation and product control. One emerging technology that shows great promise for future in-line food sensor systems is Raman spectroscopy. The overall goal of this thesis was to elucidate the feasibility of Raman spectroscopy as a tool for detailed quality evaluation of heterogeneous food raw materials, under in-line industrial conditions. To this end, two main application areas were chosen, including A1) in-line measurements of fatty acid features in salmon fillets and A2) in-line characterization of a poultry rest raw material stream. A central element in both application areas was the use of a Wide Area Illumination (WAI) Raman probe to obtain representative measurements of the heterogeneous raw materials and to tackle variations in working distance. Variations in working distance may easily happen in an industrial process line with samples of varying thicknesses and streams of varying production volumes. The limited measurement volume of the WAI probe was increased by scanning over the sample surface. We showed that this strategy was successful with respect to obtaining representative measurements. This was demonstrated through obtaining good performances for EPA+DHA estimation in salmon fillets of varying thickness (± 1 cm) and through characterization (fat, protein, bone and collagen) of poultry rest raw material with larger variations in working distances (± 3 cm). For the latter study, the method was also tested in-line at a real hydrolysis facility with promising results. For the study on salmon fillets, the varying fat deposition across the fillets was shown to have implication for choice of scanning strategy at shorter exposure times due to impact on signal-to-noise ratio (SNR). This illustrates the importance of considering the heterogeneity of the food product in a given application, and of optimizing measurement strategies accordingly. Another main objective was to elucidate the ability of Raman measurements to tackle short exposure times. This is of particular importance for measurements of single samples at a conveyor belt, where exposure time is strictly limited. This was investigated in paper I and II, where we measured single salmon and poultry samples at exposure times down to 1 s. While exposure times around 2-1 s in these cases did give acceptable performances, it was evident that these low exposure times reduced SNR and performance and that SNR was a critical parameter. This indicates that at shorter exposure times, the surface scanning with theWAI Raman probe might be less robust with respect to tackling samples of varying sample sizes or lower analyte concentrations. Therefore, for such single samples, WAI Raman spectroscopy is currently better suited for fast at-line or on-line measurements. However, such measurements could also have high value for the industry, as it represents a frequent quality feedback, which is currently lacking. Overall, it was found that further efforts on calibration development, SNR optimization and practical measurement setup are needed to unlock the full potential for in-line measurements in the two application areas. Still, this thesis has shown that it is feasible to use a WAI Raman probe for detailed characterization of very heterogeneous streams of raw material, at industrially relevant speeds and in presence of moderate variations in working distance and probe tilt. It was shown that WAI Raman spectroscopy is promising, both for measurements of continuous raw material streams and single food products on a conveyor belt. This introduces many new application opportunities for Raman spectroscopy within quality documentation, sorting, process analysis and real-time process control in the food industry.En stor utfordring for matindustrien er å håndtere store strømmer av råvarer og produkter av forskjellig opprinnelse og kvalitet på en effektiv måte. Sensorsystemer som kan brukes direkte på prosesslinjene, såkalt ”in-line”, kan potensielt måle og samle kritisk informasjon om matkvalitet og mattrygghet. Resultatet er verktøy for sortering, produktdifferensiering, prosessoptimering og produktkontroll. Raman spektroskopi er en lovende teknologi under utvikling med stort potensiale som sensorsystem i matindustrien. Målet med dette doktorgradsprosjektet var å undersøke mulighetene for å bruke Raman-spektroskopi som et verktøy for kvalitetsmålinger av heterogene matråvarer direkte i prosesslinjen. For å nå dette målet ble to bruksområder valgt, inkludert A1) in-line målinger av fettsyreprofil i laksefileter og A2) in-line karakterisering av råvarestrømmer fra fjærfe-produksjon. Et sentralt tema for begge bruksområdene var bruken av en Raman-probe med bredt belysningsområde (WAI) for å oppnå representative målinger av heterogene råvarer og for å takle variasjoner i arbeidsavstand. Variasjoner i arbeidsavstand kan fort oppstå i en industriell prosesslinje med prøver av varierende tykkelse og for stømmer med varierende produksjonsvolum. Fokusvolumet til WAI-proben ble økt ved å skanne over prøveoverflaten. Vi viste at denne strategien fungerte godt for å oppnå representative målinger. Dette ble demonstrert ved å oppnå lave prediksjonsfeil for EPA + DHA-estimering i laksefileter med varierende tykkelse (± 1 cm) og for karakterisering (fett, protein, bein og kollagen) av kyllingråstoff med større variasjoner i arbeidsavstand (± 3 cm). For sistnevnte studie ble metoden også testet in-line på et industrielt hydrolyseanlegg, med lovende resultater. For studien på laksefileter ble det vist at det varierende fettinnholdet på filletoverflaten hadde betydning for valg av skannestrategi ved kortere eksponeringstider, grunnet effekten på signal-støy-forholdet. Dette illustrerer hvor viktig det er å gjøre nøye vurderinger av heterogeniteten til et gitt matprodukt, og å optimalisere målestrategien deretter. Et annet hovedmål var å undersøke hvordan Raman-målingene håndterte kortere eksponeringstider. Dette er av spesiell betydning for målinger av enkeltprøver på et transportbelte, der eksponeringstiden er sterkt begrenset. Dette ble undersøkt i artikkel I og II, der vi målte enkeltprøver av laks og fjærfe-restråstoff ved eksponeringstider ned til 1 s. Selv om eksponeringstider rundt 2-1 s i disse tilfellene ga akseptable prediksjonsfeil, var det tydelig at disse lave eksponeringstidene reduserte signal-støy-forholdet og dermed prediksjons-prestasjonen. Signalstøy- forholdet er altså en kritisk faktor, og dette indikerer at skanning med WAI Raman-proben kan være mindre robust når det gjelder å håndtere prøver med varierende prøvestørrelser eller lavere analytt-konsentrasjoner, ved slike korte eksponeringstider. Derfor er Raman-målingene foreløpig bedre egnet for hurtige målinger ved siden av produksjonslinjen (”at-line” eller ”on-line”), for enkeltprøver. Slike målinger kan også ha høy verdi for industrien, da det representerer et system som gir hyppig tilbakemelding på kvalitet, noe som det for øyeblikket ikke finnes løsninger for. En videre innsats innen kalibreringsutvikling, SNR-optimering og utvikling av praktisk måleoppsett er nødvendig for å realisere det fulle potensialet for in-line Raman-målinger i de to applikasjonsområdene. Likevel har dette doktorgradsprosjektet vist at det er mulig å bruke en Raman probe med bredt belysningsområde til detaljert karakterisering av av svært heterogene strømmer med råvaremateriale, ved industrielt relevante eksponeringstider og med moderat variasjon i arbeidsavstand. Det ble vist at WAI Raman spektroskopi er lovende både for målinger på kontinuerlige råvarestrømmer og enkeltprøver på et transportbelte. Dette muliggjør en rekke nye applikasjoner for WAI Raman spektroskopi innen kvalitetsdokumentasjon, sortering, prosessanalyse og sanntids prosesskontroll i matindustrien

Real-time optical manipulation of cardiac conduction in intact hearts

Optogenetics has provided new insights in cardiovascular research, leading to new methods for cardiac pacing, resynchronization therapy and cardioversion. Although these interventions have clearly demonstrated the feasibility of cardiac manipulation, current optical stimulation strategies do not take into account cardiac wave dynamics in real time. Here, we developed an all‐optical platform complemented by integrated, newly developed software to monitor and control electrical activity in intact mouse hearts. The system combined a wide‐field mesoscope with a digital projector for optogenetic activation. Cardiac functionality could be manipulated either in free‐run mode with submillisecond temporal resolution or in a closed‐loop fashion: a tailored hardware and software platform allowed real‐time intervention capable of reacting within 2 ms. The methodology was applied to restore normal electrical activity after atrioventricular block, by triggering the ventricle in response to optically mapped atrial activity with appropriate timing. Real‐time intraventricular manipulation of the propagating electrical wavefront was also demonstrated, opening the prospect for real‐time resynchronization therapy and cardiac defibrillation. Furthermore, the closed‐loop approach was applied to simulate a re‐entrant circuit across the ventricle demonstrating the capability of our system to manipulate heart conduction with high versatility even in arrhythmogenic conditions. The development of this innovative optical methodology provides the first proof‐of‐concept that a real‐time optically based stimulation can control cardiac rhythm in normal and abnormal conditions, promising a new approach for the investigation of the (patho)physiology of the heart

In-line Raman spectroscopy for characterization of an industrial poultry raw material stream

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