23 research outputs found
Imported Infectious Disease and Purpose of Travel, Switzerland
Travelers who visited friends or relatives were more likely to receive a diagnosis of malaria or viral hepatitis than those who traveled for other reasons
Dealloying of Platinum-Aluminum Thin Films Part II. Electrode Performance
Highly porous Pt/Al thin film electrodes on yttria stabilized zirconia
electrolytes were prepared by dealloying of co-sputtered Pt/Al films. The
oxygen reduction capability of the resulting electrodes was analyzed in a solid
oxide fuel cell setup at elevated temperatures. During initial heating to 523 K
exceptionally high performances compared to conventional Pt thin film
electrodes were measured. This results from the high internal surface area and
large three phase boundary length obtained by the dealloying process. Exposure
to elevated temperatures of 673 K or 873 K gave rise to degradation of the
electrode performance, which was primarily attributed to the oxidation of
remaining Al in the thin films.Comment: 5 pages, 4 figure
Dealloying of Platinum-Aluminum Thin Films Part I. Dynamics of Pattern Formation
Applying focused ion beam (FIB) nanotomography and Rutherford backscattering
spectroscopy (RBS) to dealloyed platinum-aluminum thin films an in-depth
analysis of the dominating physical mechanisms of porosity formation during the
dealloying process is performed. The dynamical porosity formation due to the
dissolution of the less noble aluminum in the alloy is treated as result of a
reaction-diffusion system. The RBS analysis yields that the porosity formation
is mainly caused by a linearly propagating diffusion front, i.e. the
liquid/solid interface, with a uniform speed of 42(3) nm/s when using a 4M
aqueous NaOH solution at room temperature. The experimentally observed front
evolution is captured by the normal diffusive
Fisher-Kolmogorov-Petrovskii-Piskounov (FKPP) equation and can be interpreted
as a branching random walk phenomenon. The etching front produces a gradual
porosity with an enhanced porosity in the surface-near regions of the thin film
due to prolonged exposure of the alloy to the alkaline solution.Comment: 4 pages, 5 figure
Hillock formation of Pt thin films on Yttria stabilized Zirconia single crystals
The stability of a metal thin films on a dielectric substrate is conditioned
by the magnitude of the interactive forces at the interface. In the case of a
non-reactive interface and weak adhesion, the minimization of free surface
energy gives rise to an instability of the thin film. In order to study these
effects, Pt thin films with a thickness of 50 nm were deposited via ion-beam
sputtering on yttria stabilized zirconia single crystals. All Pt films were
subjected to heat treatments up to 973 K for 2 h. The morphological evolution
of Pt thin films has been investigated by means of scanning electron microscopy
(SEM), atomic force microscopy (AFM) and standard image analysis techniques.
Three main observations have been made: i) the deposition method has a direct
impact on the morphological evolution of the film during annealing. Instead of
hole formation, that is typically observed as response to a thermal treatment,
anisotropic pyramidal shaped hillocks are formed on top of the film. ii) It is
shown by comparing the hillocks' aspect ratio with finite element method (FEM)
simulations that the hillock formation can be assigned to a stress relaxation
process inside the thin film. iii) By measuring the equilibrium shapes and the
shape fluctuations of the formed Pt hillocks the anisotropy of the step free
energy and its stiffness have been derived in addition to the anisotropic kink
energy of the hillock's edges.Comment: 8 pages, 7 figure
Temperature-dependent 2D-3D growth transition of ultra-thin Pt films deposited by PLD
During the growth of metal thin films on dielectric substrates at a given
deposition temperature T, the film's morphology is conditioned by the magnitude
and asymmetry of up- and downhill diffusion. Any severe change of this
mechanism leads to a growth instability, which induces an alteration of the
thin film morphology. In order to study this mechanism, ultra-thin Pt films
were deposited via pulsed laser deposition (PLD) onto
yttria-stabilized-zirconia single crystals at different deposition
temperatures. The morphological evolution of Pt thin films has been
investigated by means of scanning electron microscopy (SEM), atomic force
microscopy (AFM) and standard image analysis techniques. The experimentally
obtained morphologies are compared to simulated thin film structures resulting
from a two-dimensional kinetic Monte Carlo (KMC) approach. Two main
observations have been made: i) Thin Pt films deposited onto zirconia undergo a
growth transition from two-dimensional to three-dimensional growth at T > 573
K. The growth transition and related morphological changes are a function of
the deposition temperature. ii) A critical cluster size of i\ast = 4 in
combination with an asymmetric Ehrlich-Schwoebel (ES) barrier favoring the
uphill diffusion of atoms allows for a computational reproduction of the
experimentally obtained film morphologies.Comment: 7 pages, 6 figures, 1 tabl
Cost-effectiveness analysis of malaria chemoprophylaxis for travellers to West-Africa
BACKGROUND: The importation of malaria to non-endemic countries remains a major cause of travel-related morbidity and a leading cause of travel-related hospitalizations. Currently they are three priority medications for malaria prophylaxis to West Africa: mefloquine, atovaquone/proguanil and doxycycline. We investigate the cost effectiveness of a partial reimbursement of the cheapest effective malaria chemoprophylaxis (mefloquine) for travellers to high risk areas of malaria transmission compared with the current situation of no reimbursement. METHODS: This study is a cost-effectiveness analysis based on malaria cases imported from West Africa to Switzerland from the perspective of the Swiss health system. We used a decision tree model and made a literature research on the components of travel related malaria. The main outcome measure was the cost effectiveness of malaria chemoprophylaxis reimbursement based on malaria and deaths averted. RESULTS: Using a program where travellers would be reimbursed for 80% of the cost of the cheapest malaria chemoprophylaxis is dominant (i.e. cost saving and more effective than the current situation) using the assumption that currently 68.7% of travellers to West Africa use malaria chemoprophylaxis. If the current usage of malaria chemoprophylaxis would be higher, 82.4%, the incremental cost per malaria case averted is € 2'302. The incremental cost of malaria death averted is € 191'833.The most important factors influencing the model were: the proportion of travellers using malaria chemoprophylaxis, the probability of contracting malaria without malaria chemoprophylaxis, the cost of the mefloquine regimen, the decrease in the number of travellers without malaria chemoprophylaxis in the reimbursement strategy. CONCLUSIONS: This study suggests that a reimbursement of 80% of the cost of the cheapest effective malaria chemoprophylaxis (mefloquine) for travellers from Switzerland to West Africa is highly effective in terms of malaria cases averted and is cost effective to the Swiss health system. These data are relevant to discussions about the cost effectiveness of malaria chemoprophylaxis reimbursement for vulnerable groups such as those visiting friends and relatives who have the highest risk of malaria, who are least likely to use chemoprophylaxis
Transformation of the released asbestos, carbon fibers and carbon nanotubes from composite materials and the changes of their potential health impacts
Abstract Composite materials with fibrous reinforcement often provide superior mechanical, thermal, electrical and optical properties than the matrix. Asbestos, carbon fibers and carbon nanotubes (CNTs) have been widely used in composites with profound impacts not only on technology and economy but also on human health and environment. A large number of studies have been dedicated to the release of fibrous particles from composites. Here we focus on the transformation of the fibrous fillers after their release, especially the change of the properties essential for the health impacts. Asbestos fibers exist in a large number of products and the end-of-the-life treatment of asbestos-containing materials poses potential risks. Thermal treatment can transform asbestos to non-hazardous phase which provides opportunities of safe disposal of asbestos-containing materials by incineration, but challenges still exist. Carbon fibers with diameters in the range of 5–10 μm are not considered to be respirable, however, during the release process from composites, the carbon fibers may be split along the fiber axis, generating smaller and respirable fibers. CNTs may be exposed on the surface of the composites or released as free standing fibers, which have lengths shorter than the original ones. CNTs have high thermal stability and may be exposed after thermal treatment of the composites and still keep their structural integrity. Due to the transformation of the fibrous fillers during the release process, their toxicity may be significantly different from the virgin fibers, which should be taken into account in the risk assessment of fiber-containing composites