Biomedical subjects

M Aldén

Publications and source records attributed to M Aldén.

13 recordsLinked to original sources

PubMed2004

Polarization spectroscopy applied to the detection of trace constituents in sooting combustion.

The potential of polarization spectroscopy for the detection of trace constituents in sooting combustion was investigated. It was demonstrated that the directionality of the polarization spectroscopy signal can be exploited to efficiently suppress incoherent interferences, e.g., Rayleigh scattering at soot particles. We also show how polarization spectroscopy compares with laser-induced fluorescence in this type of environment by applying both techniques to atmospheric-pressure, premixed propane/oxygen flames. The acquired signals were spatially resolved along the centerline of the flame, and measurements were conducted at several heights above the burner head and for medium to very high fuel-to-oxidizer ratios. Through our work we found that polarization spectroscopy can be applied even in the presence of large soot fractions. For most conditions, where laser-induced fluorescence suffered from interferences like elastic scattering, spatially filtered polarization spectroscopy signals were virtually background-free, and only for high soot loads did a noticeable background on the latter signal appear. This background likely stems from Mie scattering at very large soot particles.

Journal Article↗

PubMed1999

Solid state studies of drug-cyclodextrin inclusion complexes in PEG 6000 prepared by a new method.

The melting method was investigated as a possible method for producing drug-cyclodextrin (CD) inclusion compounds in a carrier. Various solid dispersions of alpha-, beta- and gamma-CD in polyethylene glycol (PEG) 6000 with and without the addition of 5% w/w indomethacin or griseofulvin were prepared using the original components. Characterisations of the samples included X-ray powder diffraction, modulated-temperature differential scanning calorimetry and dissolution tests by the paddle method according to USP XXI standard. Evidence of a complex between indomethacin and beta-CD in PEG 6000 was found. An indomethacin-gamma-CD complex formed a well defined phase in the PEG carrier, with tetragonal structure and unit cell parameters a=23.885(35) A and c=23.181(64) A. No complexation of indomethacin with alpha-CD, or with griseofulvin and beta-CD could be detected. It is suggested that competition between PEG and the drug for the binding to different CDs along with varying patterns of water loss from the CDs influence the inclusion reaction. The formation of complexes was accompanied by a decrease in the relative crystallinity of the dispersions. Dissolution tests showed that the CDs have a delaying effect on the release of indomethacin from PEG 6000 in the order alpha-CD<gamma-CD</=beta-CD.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1997

Effect of temperature history on the freeze-thawing process and activity of LDH formulations.

PURPOSE: The purpose of the study was to investigate the effect of freeze-thawing processes with different temperature histories on thermal transformations and on protein activity of lactate dehydrogenase (LDH) formulations. Polyethylene glycol (PEG 6000) and maltodextrin were used as cryoprotectants. METHODS: The thermal characterization was made by oscillating DSC (ODSC). LDH activity assays were performed spectrophotometrically. RESULTS: The crystallization of the solutions and the melting of the frozen samples occurred at fairly constant heat of crystallisation and heat of fusion values and temperatures. The main difference between the two investigated temperature cycles was an exothermic peak at -45 degrees C, which might reflect the transition between the cubic and hexagonal ice structures. When PEG was added to the system an additional endothermic peak appeared at -15 degrees C in the heating program. It was transformed into the shape of a glass transition at the same temperature when the heating rate was increased. The degree of crystallinity of the samples was evaluated as the quota between the Cp component of heat of transformation and the total heat of transformation values. Only minor differences between the two temperature histories and between the samples were observed. The cp component of the melting endotherm revealed a complex melting process with two overlapping endothermic transformations. The good protein protecting ability of PEG obtained when cooling and heating rate was low, was greatly reduced with increasing rate. The addition of maltodextrin to PEG-containing solutions lowered the activity recovery. CONCLUSIONS: The endothermic transformation of a PEG-ice structure at -15 degrees C in the heating process is strongly correlated to the protective ability of PEG 6000 in the freeze-thawing process of LDH. To obtain the highest protein activity after the freeze-thawing process, the formulation shall be transformed by a low cooling and heating rate. The crystallinity of the system melting at about 2 degrees C is independent of temperature history. The cp component of the melting endotherm, however, shows a complex transformation, where two phases of different crystallinity and stability might be involved.

Calorimetry, Differential Scanning↗

PubMed1996