118 research outputs found
Low-surface energy surfactants with branched hydrocarbon architectures
International audienceSurface tensiometry and small-angle neutron scattering have been used to characterize a new class of low-surface energy surfactants (LSESs), "hedgehog" surfactants. These surfactants are based on highly branched hydrocarbon (HC) chains as replacements for environmentally hazardous fluorocarbon surfactants and polymers. Tensiometric analyses indicate that a subtle structural modification in the tails and headgroup results in significant effects on limiting surface tensions Îłcmc at the critical micelle concentration: a higher level of branching and an increased counterion size promote an effective reduction of surface tension to low values for HC surfactants (Îłcmc 24 mN m-1). These LSESs present a new class of potentially very important materials, which form lamellar aggregates in aqueous solutions independent of dilution
Programming of metabolic effects in C57BL/6JxFVB mice by in utero and lactational exposure to perfluorooctanoic acid
Perfluorooctanoic acid (PFOA) is known to
cause developmental toxicity and is a suggested endocrine
disrupting compound (EDC). Early life exposure
to EDCs has been implicated in programming of the
developing organism for chronic diseases later in life.
Here we study perinatal metabolic programming by
PFOA using an experimental design relevant for human
exposure. C57BL/6JxFVB hybrid mice were exposed
during gestation and lactation via maternal feed to
seven low doses of PFOA at and below the NOAEL
used for current risk assessment (3–3000 μg/kg body
weight/day). After weaning, offspring were followed
for 23–25 weeks without further exposure. Offspring
showed a dose-dependent decrease in body weight from
postnatal day 4 to adulthood. Growth under high fat
diet in the last 4–6 weeks of follow-up was increased
in male and decreased in female offspring. Both sexes
showed increased liver weights, hepatic foci of cellular
alterations and nuclear dysmorphology. In females, reductions in perigonadal and perirenal fat pad weights,
serum triglycerides and cholesterol were also observed.
Endocrine parameters, such as glucose tolerance, serum
insulin and leptin, were not affected. In conclusion,
our study with perinatal exposure to PFOA in mice
produced metabolic effects in adult offspring. This is
most likely due to disrupted programming of metabolic
homeostasis, but the assayed endpoints did not provide
a mechanistic explanation. The BMDL of the programming
effects in our study is below the current point of
departure used for calculation of the tolerable daily
intake.The authors wish to acknowledge the support of
the biotechnicians from the team of Hans Strootman at the RIVM animal
facilities. Further technical support was provided by Piet Beekhof,
Hennie Hodemaekers, Sandra Imholz (RIVM), Mirjam Koster
(UU), Stefan van Leeuwen (RIKILT), Jacco Koekkoek and Marja
Lamoree (VU). This study was funded by the European Community’s
Seventh Framework Programme [FP7/2007–2013] under grant agreement
OBELIX 227391
RAILROADS IN GREECE: HISTORY, CHARACTERISTICS, AND FORECASTS
Greece was relatively tardy in implementing a national rail network. The Greek Railways Organization (OSE) was formed in 1970 and united a number of regional railroads, some dating back to 1884. The current rail network in Greece has a length of approximately 2500 km with standard- and metric-gage tracks. Disadvantages of the network include a high percentage of single-line track, lack of homogeneity of track gage, inefficient alignment, absence of intermodal connections, and many at-grade intersections. Advantages include double tracks in a significant part of the Athens-Thessalonica axis that serves more than half of Greece\u27s population, improved operational controls, and popular intercity trains offering speedy service. Factors that affect railroad passenger and freight volumes include competition from airlines and motor carriers, gas prices, inflation, and the gross national product. These factors were used to estimate time-series models. Forecasts indicate increasing passenger demand and decreasing freight demand. OSE could provide a valuable and viable passenger service if cost-effective expenditures for improving it are possible. The future of freight operations is not hopeful. Additional emphasis may be placed on lines with historical and cultural significance. Further study is needed to assess the sustainability of forecasts vis-a-vis actual market shares and costs
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