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| 2. |
- Ström, Daniel, 1971, et al.
(författare)
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A new device for coating single particles under controlled conditions
- 2005
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 60, s. 4647-4653
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Tidskriftsartikel (refereegranskat)abstract
- A new device for coating a single levitated particle in a controllable environment is designed and tested. This enables fluidized bed processing to be simulated experimentally on a single-particle level. The device consists of a coating chamber, which contains a capillary tube for levitating the particle, a micro-dispenser for producing discrete drops of controlled size and velocity and a device for supplying gas with specified temperature and humidity. The coating chamber consists of two parts, a confined space where the particle is levitated and a droplet insertion cone where the coating solution is injected into the particle suspending gas flow. A capillary with a well-defined diameter connects the droplet insertion cone and the area where the particle is levitated. The device is equipped with a piezo-actuated flow-through micro-dispenser that has the ability to produce discrete droplets with high reproducibility in terms of droplet size and velocity. The gas required for the coating process is taken from a gas container where the water content is analysed and kept at a minimum. A liquid flow is then introduced into the gas flow at a well-defined flow rate, mixed and evaporated in a three-way mixing vault. The humidified gas flow is then split into two separate flows; a suspending gas flow and a protecting gas flow for the inside of the coating chamber. The device is equipped with a high-speed video camera for monitoring both droplet production and droplet impact. Temperatures and flow rates throughout the device are measured and logged. Preliminary results show the influence of solvent, gas quality and coating procedure on the quality of the coating.
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| 3. |
- Abrahamsson, Christoffer, et al.
(författare)
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Scatter correction of transmission near-infrared spectra by photon migration data: Quantitative analysis of solids
- 2005
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Ingår i: Applied Spectroscopy. - 1943-3530. ; 59:11, s. 1381-1387
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Tidskriftsartikel (refereegranskat)abstract
- The scope of this work is a new methodology to correct conventional near-infrared (NIR) data for scattering effects. The technique aims at measuring the absorption coefficient of the samples rather than the total attenuation measured in conventional NIR spectroscopy. The main advantage of this is that the absorption coefficient is independent of the path length of the light inside the sample and therefore independent of the scattering effects. The method is based on time-resolved spectroscopy and modeling of light transport by diffusion theory. This provides an independent measure of the scattering properties of the samples and therefore of the path length of light. This yields a clear advantage over other preprocessing techniques, where scattering effects are estimated and corrected for by using the shape of the measured spectrum only. Partial least squares (PLS) calibration models show that, by using the proposed evaluation scheme, the predictive ability is improved by 50% as compared to a model based on conventional NIR data alone. The method also makes it possible to predict the concentration of active substance in samples with other physical properties than the samples included in the calibration model.
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| 4. |
- Abrahamsson, Christoffer, et al.
(författare)
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Time and wavelength resolved spectroscopy of turbid media using light continuum generated in a crystal fiber
- 2004
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Ingår i: Optics Express. - 1094-4087. ; 12:17, s. 4103-4112
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel system for time-resolved diffuse remission spectral measurements, based on short light continuum pulses generated in an index-guided crystal fiber, and a spectrometer-equipped streak camera. The system enables spectral recordings of absorption and reduced scattering coefficients of turbid media in the wavelength range 500 - 1200 nm with a spectral resolution of 5 nm and a temporal resolution of 30 ps. The optical properties are calculated by fitting the solution of the diffusion equation to the time-dispersion curve at each wavelength. Example measurements are presented from an apple, a finger and a pharmaceutical tablet. (C) 2004 Optical Society of America.
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| 5. |
- Abrahamsson, Christoffer, et al.
(författare)
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Time-resolved NIR spectroscopy for quantitative analysis of intact pharmaceutical tablets
- 2005
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 77:4, s. 1055-1059
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Tidskriftsartikel (refereegranskat)abstract
- Near-infrared (NIR) spectroscopy is a useful technique for quantitative measurements of intact tablets, but it suffers from limitations due to the fact that changes in the physical properties of a sample strongly affect the recorded spectrum. In this work, time-resolved transmission NIR spectroscopy was utilized to conduct quantitative measurements of intact tablets. The technique enables separation of the absorption properties of the sample from the scattering properties and can therefore handle changes of the physical parameters of the samples in a better way than conventional NIR transmission spectroscopy. The experiments were conducted using a pulsed Ti:sapphire laser coupled into a nonlinear photonic crystal fiber as light source. The light transmitted through the sample was measured by a time-resolving streak camera. A comparison of the results from the time-resolved technique with the results from conventional transmission NIR spectroscopy was made using tablets containing different concentrations of iron oxide and manufactured with different thicknesses. A PLS model made with data from the time-resolved technique predicted samples 5 times better than a PLS model made data from the conventional NIR transmission technique. Furthermore, an improvement to predict samples with physical properties outside those included in the calibration set was demonstrated.
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| 6. |
- Andersson, M, et al.
(författare)
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NIR spectroscopy on moving solids using a scanning grating spectrometer - impact on multivariate process analysis
- 2005
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439. ; 75:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The effect of sample movement on spectral response during fiber probe diffuse reflectance near-infrared spectrometry (NIR) sampling was characterized. This is of central importance in Process Analytical Chemistry (PAC) and Process Analytical Technology (PAT). The incitement to this study was the observation of spectral artifacts during measurements of powder samples in process streams when using a mechanically scanning spectrometer. Artifacts appeared as momentary changes in the spectral response during acquisition of a scan. These transitions emanate from continuous replacement of the sample subfraction seen by the probe and are typical for turbid media where sample properties may vary locally with respect to scattering and/or absorption. The impact on qualitative and quantitative analysis using chemometric methods such as principal component analysis (PCA) and partial least squares (PLS) regression was evaluated through experimental and theoretical simulations. It was generally found that spectra with the smallest residuals after projection onto the models came from non-moving samples or samples moving only slowly. It is shown that the magnitude of the spectral residuals is directly connected to the effective sample size, which relates both to sample speed as well as to the sample area presented to the probe. Implications for in-line/on-line process analysis of solids are discussed. (C) 2004 Elsevier B.V. All rights reserved.
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| 8. |
- Folestad, A., et al.
(författare)
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IL-17 cytokines in bone healing of diabetic Charcot arthropathy patients: a prospective 2 year follow-up study
- 2015
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Ingår i: Journal of Foot and Ankle Research. - : Springer Science and Business Media LLC. - 1757-1146. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: Little is currently known of the pathophysiological mechanisms triggering Charcot arthropathy and regulating its recovery although foot trauma has been proposed as a major initiating factor by activation of proinflammatory cytokines leading to increased osteoclastogenic activity and progressive bone destruction. Several members of the IL-17 family of proinflammatory cytokines have been shown to play a key role in the pathogenesis of inflammatory conditions affecting bone and joints but none has previously been studied in Charcot foot patients. The aim of this study was to investigate the role of IL-17A, IL-17E and IL-17F in patients presenting with Charcot foot. Methods: Twenty-six consecutive Charcot patients were monitored during 2 years by repeated foot radiographs, MRI and circulating levels of IL-17A, IL-17E and IL-17F. Analysis of cytokines was done by ultra-sensitive chemiluminescence technique and data were analyzed by one-way repeated measures ANOVA. Neuropathic diabetic patients (n = 20) and healthy subjects (n = 20) served as controls. Results: Plasma IL-17A and IL-17E in weight-bearing Charcot patients at diagnosis were at the level of diabetic controls, whereas IL-17F was significantly lower than diabetic controls. A significant increase in IL-17A and IL-17E reaching a peak 2-4 months after inclusion and start of offloading treatment in Charcot patients was followed by a gradual decrease to the level of diabetic controls at 2 years postinclusion. In contrast, IL-17F increased gradually from inclusion to a level not significantly different from diabetic controls after 2 years. Conclusions: Charcot patients display a significant elevation of all three IL-17 cytokines during the follow-up period relative values at diagnosis and values in control patients supporting a role in the bone repair and remodeling activity during the recovery phase. The rapid increase of IL-17A and IL-17E shortly after initiating off-loading treatment could suggest this to be a response to immobilization and stabilization of the diseased foot.
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| 9. |
- Gradinarsky, Lubomir, 1970, et al.
(författare)
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A method for detection of powder materials in metallic hollow structures using microwaves
- 2008
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Ingår i: Measurement: Journal of the International Measurement Confederation. - : Elsevier BV. - 0263-2241. ; 41:6, s. 637-646
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a method for detection of the presence of small amounts of solids (powders, granules, etc.) inside metallic structures such as process vessels and containers. The method is based on propagation of microwave electromagnetic (EM) energy inside the structures and analysing the complex reflection coefficient Gamma represented by the scattering parameter S-11. 3D EM simulations were used to predict the behaviour of S for structures of rectangular, circular, and conical shapes, contaminated with materials with weak dielectric properties. The suggested method sensitivity and the effects of the material size and its distribution were assessed and results presented of comparisons of simulations and measurements. This paper demonstrates the ability to detect very low levels of contamination, e.g. of the order of 0.01-0.03 parts of a reference vessel's volume of one (e.g. length = 1 cm, width = 0.5 cm, and height = 2 cm) for materials with weak dielectric properties. This sensitivity is even better in terms of volume ratio (contamination/vessel's volume) for structures with bigger volumes and contaminants with stronger dielectric properties e.g. wet powders. The method is fully scalable for vessels with different sizes. Therefore industrial application of the method to physical processing of pharmaceutics, food, agriculture and others is envisioned. (C) 2007 Elsevier Ltd. All rights reserved.
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