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Jan Lindgren

Publications and source records attributed to Jan Lindgren.

6 recordsLinked to original sources
PubMed2005

Differences in binding of a cationic surfactant to cross-linked sodium poly(acrylate) and sodium poly(styrene sulfonate) studied by Raman spectroscopy.

Raman spectroscopy has been used to investigate the structure of gel-surfactant complexes. Cross-linked sodium poly(acrylate) and sodium poly(styrene sulfonate) were immersed in solutions of the cationic surfactant dodecyl trimethylammonium bromide. During the deswelling process, two distinct regions could be observed for both types of gels. Looking at the Raman spectra, however, for the poly(styrene sulfonate), the surfactant could be found throughout the gel particle, whereas for poly(acrylate), essentially all the surfactant was bound in a surface layer.

Acrylic Resins↗
PubMed2003

Ligand distributions in agarose particles as determined by confocal Raman spectroscopy and confocal scanning laser microscopy.

Confocal Raman spectroscopy and confocal scanning laser microscopy have been used to analyze ligand distributions within individual chromatographic adsorbent particles. Three different types of particles have been investigated. The first type was synthesized to have a uniform distribution of allyl groups, whereas the two others were designed to have a surface layer of sulphopropyl groups and cores containing allyl groups and dextran, respectively. With confocal Raman spectroscopy it was possible to follow the distribution of both the surface layer and the interior. The distribution of sulphopropyl groups was evaluated with both confocal scanning laser microscopy and confocal Raman spectroscopy, whereas the distributions of allyl groups and dextran were evaluated only with the latter method. The results from the confocal measurements showed the expected result with a uniform distribution of allyl groups in the first type of particle and surface layers of sulphopropyl groups and cores with dextran or allyl groups for the two others.

Adsorption↗
PubMed2002

Protection mechanism of Tween 80 during freeze-thawing of a model protein, LDH.

The purpose of the study was to investigate the protective mechanism of a non-ionic surfactant, Tween 80, at freeze-thawing with controlled temperature history of a model protein, lactate dehydrogenase (LDH). The system was examined by differential scanning calorimetry (DSC) and infrared spectroscopy (IR). LDH activity assays were performed spectrophotometrically. In all samples, independent of temperature history and addition of surfactant, all water was crystallized to polycrystalline ice at temperatures below -20 degrees C. The size and perfection of the ice crystals could be varied by a range of cooling rates giving different degrees of undercooling. At Tween concentrations below the cmc at crystallization, lower concentrations were required at low cooling rates compared to higher cooling rates to protect LDH. Concentrations above cmc of Tween reduced the protection at a cooling rate of 5 degrees C min(-1) and at quenching in N(2)(l). The amount of Tween needed for complete protection correlated to the surface area of the ice crystals at a certain temperature history. Tween 80 protects LDH from denaturation at freeze-thawing by hindering its destructive interaction with the ice crystals. The protective effect might be obtained when Tween molecules compete with the protein for sites on the ice surface. The optimum concentration of Tween needed for complete protection is dependent on the temperature history.

Cold Temperature↗
PubMed2002

Indwelling catheters used from the onset of diabetes decrease injection pain and pre-injection anxiety.

OBJECTIVES: To investigate the use of indwelling catheters as injection aids at diabetes onset to reduce injection pain and pre-injection anxiety. STUDY DESIGN: Forty-one patients aged 8.1 +/- 3.7 years (range, 1-15) participated in this open, controlled randomized study. A 10-cm VAS with faces was used for scoring. A local anesthetic cream was used before all insertions. The control group used insulin pens with standard needles. After one week, the indwelling catheter group could choose regular injections but were included in the "intention to treat" analysis. RESULTS: Injection pain and anxiety decreased from day 1 to 15 in both groups (average, 4.1 injections/day). Pain was significantly lower for indwelling catheter injections when scored by parents (median, 1.2 cm vs 2.7 cm; P =.002), children/teenagers (0.8 cm vs 1.5 cm; P =.006), and nurses (1.4 cm vs 3.0 cm; P =.002). Parental pre-injection anxiety was also lower (1.2 cm vs 2.9 cm; P =.016). Taking injections, including inserting catheters, was found to be less problematic with an indwelling catheter (1.6 cm vs 3.3 cm;P =.009). During the 6-month follow-up, injection pain and injection problems were significantly lower in the catheter group. Mean catheter indwelling time was 3.7 days. Median pain for catheter insertion was 2.1 cm and for glucose testing was 0.9 cm. Sixteen of 20 patients continued to use indwelling catheters after 2 weeks, and 9 of 20 after 6 months. CONCLUSIONS: We found an evident relief of pre-injection anxiety and injection pain when using indwelling catheters for introducing insulin injections at the onset of diabetes.

Adolescent↗