| 1. |
- Alin, Jonas
(författare)
-
Microwave heating effects on degradation and migration of additives from polypropylene packaging
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The effect of different food types, polymer qualities and microwaves on the overall and specific migration during microwave heating of plastic packaging was investigated to better understand the packaging-food interactions and the effect of microwaves on food packaging. This work focuses on the migration of chemical compounds to food simulants from commercially available polypropylene packages. Packages used were made of polypropylene homopolymer (PP), co-polymer (PP-C) and random co-polymer (PP-R). Polymers matrix changes were monitored by following possible changes in crystallinity after microwave heating. Antioxidants Irgafos 168 and Irganox 1010 were present in all the three PP packages. Other volatiles, primarily degradation products of antioxidants, were also detected and identified in the unaged packages. Significant antioxidant degradation took place during microwave heating of the packages in the fatty food simulants 90/10 isooctane/ethanol and ethanol resulting in the formation and migration of degradation products while no degradation of antioxidants was detected during conventional heating of the packages in the fatty food simulants. Antioxidant Irgafos 168 and Irganox 1010 migration rates were otherwise similar during microwave heating as during conventional heating to the fatty food simulants and antioxidant diffusion coefficients were similar to earlier established values obtained during conventional heating. Antioxidant migration rates from the three polymers to fatty food simulants differed largely with respect to PP type and increased with decreasing degree of crystallinity in the materials, PP-R showing the highest migration rate. Swelling in isooctane food simulant caused the antioxidant diffusion coefficients to increase by factors of 100-1000 at 80 ºC and decreased the temperature dependence of antioxidant migration. It also increased the overall migration to above established overall migration limits during both microwave and conventional heating. Electrospray ionization mass spectrometry (ESI-MS) was shown to be a valuable new tool for additive migration analysis of compounds not detectable by HPLC or GC-MS.
|
|
| 2. |
- Katzeff, Cecilia, 1957-, et al.
(författare)
-
Exploring Sustainable Practices in Workplace Settings through Visualizing Electricity Consumption
- 2013
-
Ingår i: ACM Transactions on Computer-Human Interaction. - New York : ACM Press. - 1073-0516 .- 1557-7325. ; 20:5
-
Tidskriftsartikel (refereegranskat)abstract
- People’s domestic habits are increasingly being targeted to reduce levels of CO2 emissions. Whereas domestic energy consumption has received a lot of attention with several reported studies on sustainable practices, there are very few studies on workplace practices. Nevertheless, these are considered as having much potential for reducing energy consumption. This paper presents the findings from two field studies where two different types of prototypes for visualizing energy use were designed, implemented and evaluated in different types of workplace settings – factories and offices. The studies used design probes to explore how visual feedback for electricity use was interpreted and acted upon by employees in work settings. A striking observation was that it is very difficult to get people to change to more pro-environmental behavior and practices in a workplace environment. The paper discusses why this might be the case.
|
|
| 3. |
- Li, Zhilun, et al.
(författare)
-
p21-activated kinase 4 phosphorylation of integrin beta5 Ser-759 and Ser-762 regulates cell migration
- 2010
-
Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 285:31, s. 23699-23710
-
Tidskriftsartikel (refereegranskat)abstract
- Modulation of integrin alphavbeta5 regulates vascular permeability, angiogenesis, and tumor dissemination. In addition, we previously found a role for p21-activated kinase 4 (PAK4) in selective regulation of integrin alphavbeta5-mediated cell motility (Zhang, H., Li, Z., Viklund, E. K., and Strömblad, S. (2002) J. Cell Biol. 158, 1287-1297). This report focuses on the molecular mechanisms of this regulation. We here identified a unique PAK4-binding membrane-proximal integrin beta5-SERS-motif involved in controlling cell attachment and migration. We also mapped the integrin beta5-binding site within PAK4. We found that PAK4 binding to integrin beta5 was not sufficient to promote cell migration, but that PAK4 kinase activity was required for PAK4 promotion of cell motility. Importantly, PAK4 specifically phosphorylated the integrin beta5 subunit at Ser-759 and Ser-762 within the beta5-SERS-motif. Point mutation of these two serine residues abolished the PAK4-induced cell migration, indicating a functional role for these phosphorylations in migration. Our results may give important leads to the functional regulation of integrin alphavbeta5, with implications for vascular permeability, angiogenesis, and cancer dissemination.
|
|
| 4. |
- Svensson, Frida, 1980, et al.
(författare)
-
Lipophilic ruthenium complexes with tuned cell membrane affinity and photoactivated uptake
- 2010
-
Ingår i: Biophysical Chemistry. - : Elsevier BV. - 1873-4200 .- 0301-4622. ; 149:3, s. 102-106
-
Tidskriftsartikel (refereegranskat)abstract
- Ruthenium dipyridophenazine (dppz) complexes are virtually non-emissive in aqueous solutions but show strong luminescence in hydrophobic environments, making them interesting as molecular probes in cellular imaging. We show by luminescence spectroscopy that by substituting the dppz ligand with alkyl ether chains of increasing length the complexes can be tuned from preferential intercalation into DNA to insertion in model phospholipid membranes Confocal laser scanning microscopy (CLSM) on methanol fixed CHO-K1 cells show an analogous distribution in the cell, where the least hydrophobic complex exclusively stains the nucleus whereas the more hydrophobic ones seem to predominantly stain membrane structures in the cytoplasm In live cells CLSM show that initially only the more hydrophobic derivatives stain the plasma membrane However, brief further exposure to the laser light causes permeabilization of the membrane and accumulation of extracellular ruthenium complexes in internal cellular structures, similarly to the distribution found in fixed cells. (C) 2010 Elsevier B V All rights reserved
|
|
| 5. |
- Xu, Huan, et al.
(författare)
-
Structural Basis for Unique Hierarchical Cylindrites Induced by Ultrahigh Shear Gradient in Single Natural Fiber Reinforced Poly(lactic acid) Green Composites
- 2014
-
Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 15:5, s. 1676-1686
-
Tidskriftsartikel (refereegranskat)abstract
- A local shear flow field was feasibly generated by pulling the ramie fiber in single fiber reinforced poly(lactic acid) (PLA) composites. This was featured by an ultrahigh shear gradient with a maximum shear rate up to 1500 s(-1), a level comparable to that frequently occurring during the practical polymer processing. To distinguish shear-induced self-nucleation and ramie fiber-induced heterogeneous nucleation, the shear history was classified by pulling the fiber for 5 s (pulled sample) and pulling out the fiber during 10 s (pulled-out sample), while the static fiber-induced crystallization was carried out as the counterpart. As a result of the ultrahigh shear gradient, the combination of primary shear-induced nucleation in the central region and secondary nucleation in the outer layer assembled the unique hierarchical superstructures. By comparing the architectural configurations of interphases formed in the static, pulled, and pulled-out samples, it was shown that the hierarchical cylindrites underwent the process of self-nucleation driven by the applied shear flow, very different from the formation of fiber-induced transcrystallinity (TC) triggered by the heterogeneous nucleating sites at the static fiber surface. The twisting of transcrystallized lamellae may take place due to the spatial hindrance induced by the incredibly dense nuclei under the intense shearing flow, as observed in the synchrotron X-ray diffraction patterns. The influence of chain characteristics on the crystalline morphology was further explored by adding a small amount of poly(ethylene glycol) (PEG) to enhance the molecular mobility of PLA. It was of interest to find that the existence of PEG not only facilitated the growth rates of TC and cylindrites but also improved the preferential orientation of PLA chains and thus expanded the ordered regions. We unearthed lamellar units that were composed of rich fibrillar extended chain crystals (diameter of 50-80 nm). These results are of importance to shed light on tailoring crystalline morphology for natural fibers reinforced green composite materials. Of immense practical significance, too, is the crystalline evolution that has been tracked in the simple model penetrated with an ultrahigh shear gradient, which researchers have so far been unable to replicate during the practical melt processing, such as extrusion and injection molding.
|
|
