380 research outputs found
Effects of breast feeding on neuropsychological development in a community with methylmercury exposure from seafood
Harmonic generation in ring-shaped molecules
We study numerically the interaction between an intense circularly polarized
laser field and an electron moving in a potential which has a discrete
cylindrical symmetry with respect to the laser pulse propagation direction.
This setup serves as a simple model, e.g., for benzene and other aromatic
compounds. From general symmetry considerations, within a Floquet approach,
selection rules for the harmonic generation [O. Alon Phys. Rev. Lett. 80 3743
(1998)] have been derived recently. Instead, the results we present in this
paper have been obtained solving the time-dependent Schroedinger equation ab
initio for realistic pulse shapes. We find a rich structure which is not always
dominated by the laser harmonics.Comment: 15 pages including 7 figure
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Consequences of exposure measurement error for confounder identification in environmental epidemiology
Non-differential measurement error in the exposure variable is known to attenuate the dose–response relationship. The amount of attenuation introduced in a given situation is not only a function of the precision of the exposure measurement but also depends on the conditional variance of the true exposure given the other independent variables. In addition, confounder effects may also be affected by the exposure measurement error. These difficulties in statistical model development are illustrated by examples from a epidemiological study performed in the Faroe Islands to investigate the adverse health effects of prenatal mercury exposure
Private Financing or Not, That is the Question: Lessons from the Light Rail Systems in Spain
The objective of this paper is to analyze if there
is any difference between the light rail systems in Spain
according to whether they have been carried out through
public financing or private financing (totally or partially).
The importance of this study lies in the fact that, for decades,
the public–private partnership has been proposed as
an alternative to public financing of public transport projects
in order to obtain additional financial resources,
reduce the public deficit, and increase efficiency. However,
there are hardly any detailed studies describing how these
initiatives have turned out. Therefore, the present study
analyzes if there is any difference in the main variables
explaining the performance of light rail projects in Spain
depending on their source of funding can be found. For
this, the relationship between variables related to design,
operation and costs of the projects, and the percentage of
private financing were statistically analyzed. As the most
relevant conclusion, we underline the fact that the investment
per passenger increases when financing is completely
private. This would indicate that the most cost-effective
lines, from a social standpoint, were financed totally or
partially by the public administrations, whereas the least
beneficial ones for society were assigned to private enterprises.
This finding provides an advance in the knowledge
of the consequences of private participation in the financing
of public transport projects, indicating, moreover, that
the biggest beneficiaries of this type of projects might be
the construction companies and the politicians involvedThe authors would like to thank the ERDF of
European Union for financial support via project ‘‘Herramienta para
la evaluacio´n previa de infraestructuras de transporte pu´blico’’
(GGI3003IDIE). We also thank to Public Works Agency and
Regional Ministry of Public Works and Housing of the Regional
Government of Andalusia (AOPJA) and the Ministry of Education,
Culture and Sports of the Government of Spain
On the possibility of magneto-structural correlations: detailed studies of di-nickel carboxylate complexes
A series of water-bridged dinickel complexes of the general formula [Ni<sub>2</sub>(μ<sub>2</sub>-OH<sub>2</sub>)(μ2-
O<sub>2</sub>C<sup>t</sup>Bu)<sub>2</sub>(O<sub>2</sub>C<sup>t</sup>Bu)2(L)(L0)] (L = HO<sub>2</sub>C<sup>t</sup>Bu, L0 = HO<sub>2</sub>C<sup>t</sup>Bu (1), pyridine (2),
3-methylpyridine (4); L = L0 = pyridine (3), 3-methylpyridine (5)) has been synthesized
and structurally characterized by X-ray crystallography. The magnetic properties
have been probed by magnetometry and EPR spectroscopy, and detailed measurements
show that the axial zero-field splitting, D, of the nickel(ii) ions is on the same order as
the isotropic exchange interaction, J, between the nickel sites. The isotropic exchange
interaction can be related to the angle between the nickel centers and the bridging
water molecule, while the magnitude of D can be related to the coordination sphere at
the nickel sites
Cohort studies of Faroese children concerning potential adverse health effects after the mothers’ exposure to marine contaminants during pregnancy
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Neurobehavioral performance of Inuit children with increased prenatal exposure to methylmercury
Exposure to methylmercury from marine mammals and other seafood may affect the development of the central nervous system. In a traditional Inuit community in Qaanaaq, Greenland, mercury concentrations in cord blood and maternal hair have been examined in connection with all births. We examined 43 children at age 7–12 years with a battery of neurobehavioral tests. The average mercury concentration in hair was 5.0 μ/g and 1.5 μ/g in children and mothers, respectively. Clinical neurological examination did not reveal any obvious deficits. However, neuropsychological tests showed possible exposure-associated deficits, though only in a few cases reaching statistical significance. In conjunction with data from other studies, peak latencies on brainstem auditory evoked potentials tended to be prolonged at increased exposure levels. The data from the present study therefore appears in accordance with other evidence that prenatal or early postnatal exposures to methylmercury may cause subtle neurobehavioral deficits
Rational design and direct fabrication of multi-walled hollow electrospun fibers with controllable structure and surface properties
Multi-walled hollow fibers with a novel architecture are fabricated through utilizing a direct,one-step tri-axial electrospinning process with a manufacturing methodology which does not require any post-treatments for the removal of core material for creating hollowness in the fiber structure. The hydrophilicity of both inner and outer layers’ solution needs to be dissimilar and carefully controlled for creating a two-walled/layered hollow fiber tructure
with a sharp interface. To this end, Hansen solubility parameters are used as n index of layer solution affinity hence allowing for control of diffusion across the layers and the surface porosity whereby an ideal multi-walled hollow electrospun fiber is shown to be producible by tri-axial electrospinning process. Multi-walled hollow electrospun fibers with different inner
and outer diameters and different surface morphology are successfully produced by using dissimilar material combinations for inner and outer layers (i.e., hydrophobic polymers as outer layer and hydrophilic polymer as inner layer). Upon using different material combinations for inner and outer layers, it is shown that one may control both the outer and inner diameters of the fiber. The inner layer not only acts as a barrier and thus provides an ease in the encapsulation of functional core materials of interest with different viscosities but also adds stiffness to the fiber. The structure and the surface morphology of fibers are controlled by changing applied voltage, polymer types, polymer concentration, and the evaporation rate of solvents. It is demonstrated that if the vapor pressure of the solvent for a given outer layer polymer is low, the fiber diameter decreases down to 100 nm whereas solvents with higher vapor pressure result in fibers with the outer diameter of up to 1 μm. The influence of electric field strength on the shape of Taylor cone is also monitored during the production process and the manufactured fibers are structurally investigated by relevant surface characterization techniques
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