8 research outputs found
Seafood from Norway : food safety
Since Norway is a major supplier of seafood
worldwide, monitoring the food safety of Norwegian fish
products is a priority. This commentary gives a brief
overview of the food safety of seafood from Norwegian
waters. Several preventative measures during harvest/catch,
processing and distribution have been established and
are implemented regularly. Furthermore, comprehensive
monitoring programmes to detect and quantify undesirable
substances, such as heavy metals and polychlorinated
biphenyls (PCBs), in Norwegian seafood are carried out.
Substances with health benefits, such as omega-3 fatty
acids, are also analysed. In general, evidence shows the
level of undesirable substances in seafood from Norway to
be low. In fact, in the majority of samples analysed, levels
of undesirable substances were reported to be below the
maximum limit set by the European Union (EU). This leads
to the conclusion that consumption of seafood originating
from Norway involves a low risk of negative health effects
and that consumers can have confidence in the products
they purchase.peer-reviewe
Groepsgedrag op de nanoschaal
Monodisperse gas microbubbles, encapsulated with a shell
of photopolymerizable
diacetylene lipids and phospholipids, were produced by microfluidic
flow focusing, for use as ultrasound contrast agents. The stability
of the polymerized shell microbubbles against both aggregation and
gas dissolution under physiological conditions was studied. Polyethylene
glycol (PEG) 5000, which was attached to the diacetylene lipids, was
predicted by molecular theory to provide more steric hindrance against
aggregation than PEG 2000, and this was confirmed experimentally.
The polymerized shell microbubbles were found to have higher shell-resistance
than nonpolymerizable shell microbubbles and commercially available
microbubbles (Vevo MicroMarker). The acoustic stability under 7.5
MHz ultrasound insonation was significantly greater than that for
the two comparison microbubbles. The acoustic stability was tunable
by varying the amount of diacetylene lipid. Thus, our polymerized
shell microbubbles are a promising platform for ultrasound contrast
agents
Stability of Superparamagnetic Iron Oxide Nanoparticles at Different pH Values: Experimental and Theoretical Analysis
The detection of superparamagnetic nanoparticles using
NMR logging
has the potential to provide enhanced contrast in oil reservoir rock
formations. The stability of the nanoparticles is critical because
the NMR relaxivity (<i>R</i><sub>2</sub> ⥠1/<i>T</i><sub>2</sub>) is dependent on the particle size. Here we
use a molecular theory to predict and validate experimentally the
stability of citric acid-coated/PEGylated iron oxide nanoparticles
under different pH conditions (pH 5, 7, 9, 11). The predicted value
for the critical surface coverage required to produce a steric barrier
of 5<i>k</i><sub>B</sub><i>T</i> for PEGylated
nanoparticles (MW 2000) was 0.078 nm<sup>â2</sup>, which is
less than the experimental value of 0.143 nm<sup>â2</sup>,
implying that the nanoparticles should be stable at all pH values.
Dynamic light scattering (DLS) measurements showed that the effective
diameter did not increase at pH 7 or 9 after 30 days but increased
at pH 11. The shifts in NMR relaxivity (from <i>R</i><sub>2</sub> data) at 2 MHz agreed well with the changes in hydrodynamic
diameter obtained from DLS data, indicating that the aggregation behavior
of the nanoparticles can be easily and quantitatively detected by
NMR. The unexpected aggregation at pH 11 is due to the desorption
of the surface coating (citric acid or PEG) from the nanoparticle
surface not accounted for in the theory. This study shows that the
stability of the nanoparticles can be predicted by the theory and
detected by NMR quantitatively, which suggests the nanoparticles to
be a possible oil-field nanosensor